Field
[0001] The present disclosure relates to a headphone device.
Background
[0002] In recent years, noise cancellation (NC) techniques have been widely developed. According
to the noise cancellation technique, it is possible to cancel noise by outputting
audio to reduce (that is, cancel) an external sound (noise) from a speaker.
[0003] Noise cancellation systems are often mounted on devices worn on an ear such as headphones
and an earphone. The noise cancellation system mounted in these devices are roughly
divided into a type that performs feed forward (FF) noise cancellation (hereinafter
referred to as FF-NC) and a type that performs feedback (FB) noise cancellation (hereinafter
referred to as FB-NC), or a combination type of FF-NC and FB-NC. When the FF-NC type
noise cancellation system is mounted, an FF-NC microphone is provided on an outer
side (outside) of the device. When the FB-NC type noise cancellation system is mounted,
an FB-NC microphone is provided on an inner side (space side formed by the device,
user's head, and the like) of the device. In the combination type, both the microphones
are provided. In particular, the combination type has high noise canceling performance
obtained by utilizing each characteristic of FF-NC and FB-NC, and basically, each
control can be designed independently. Therefore, the combination type noise cancellation
system is mounted on a high-end device in recent years. For example, the combination
type noise cancellation system is disclosed in the following Patent Literature 1.
[0004] In addition, there is a demand for further improvement in the noise canceling performance
regardless of the FF-NC type, the FB-NC type, or the combination type. For example,
the following Patent Literature 2 proposes a technique for suppressing influence of
a digital delay while considering a merit of digitization in a filter circuit for
FB-NC.
Citation List
Patent Literature
Summary
Technical Problem
[0006] However, the techniques disclosed in the above patent literatures have room for further
performance improvement. For example, a microphone provided in a housing of headphones
is used for a noise cancellation process in the techniques disclosed in above Patent
Literatures 1 and 2. The microphone provided in the housing of the headphones is typically
far from user's eardrum. Therefore, a point at which noise is minimized (that is,
a cancellation point) is far from the user's eardrum, and a noise canceling effect
is limited.
[0007] Therefore, the present disclosure proposes a mechanism that enables a cancellation
point in a noise cancellation process to be located closer to user's eardrum.
Solution to Problem
[0008] According to the present disclosure, a headphone device is provided that includes:
a housing; an audio input unit that is arranged to be separated from the housing and
collects audio to generate an audio signal; a holding unit that abuts on a cavum concha
or an inner wall of an ear canal of a user and holds the audio input unit in a space
closer to an eardrum side than a tragus, in a state of being worn by the user; a wired
connection unit that connects the housing and the audio input unit in a wired manner;
a signal processing unit that generates a noise cancellation signal for an external
sound based on the audio signal generated by the audio input unit, and generates an
output signal based on the generated noise cancellation signal; and an audio output
unit that outputs audio based on the output signal.
Advantageous Effects of Invention
[0009] As described above, the mechanism that enables the cancellation point in the noise
cancellation process to be located closer to the user's eardrum is provided according
to the present disclosure. Note that the above-described effect is not necessarily
limited, and any effect illustrated in the present specification or other effects
that can be grasped from the present specification may be exhibited in addition to
the above-described effect or instead of the above-described effect.
Brief Description of Drawings
[0010]
FIG. 1 is a view for describing an example of an exterior configuration of an ear
hole opening device according to a first embodiment.
FIG. 2 is a diagram illustrating an example of an internal configuration of an ear
hole opening device according to the embodiment.
FIG. 3 is a view for describing an outline of a noise cancellation process using the
ear hole opening device according to the embodiment.
FIG. 4 is a view for describing a typical human ear structure.
FIG. 5 is a view for describing noise N arriving at a human ear.
FIG. 6 is a view for describing an arrangement of a microphone in the ear hole opening
device according to the embodiment.
FIG. 7 is a view illustrating a state where the ear hole opening device according
to the embodiment is attached to a user.
FIG. 8 is a diagram illustrating a model configuration example of a noise cancellation
process of a classical control FB scheme using the ear hole opening device according
to the embodiment.
FIG. 9 is a diagram illustrating a model configuration example of a noise cancellation
process of the classical control FB scheme using a sealed noise canceling earphone
according to a comparative example.
FIG. 10 is a diagram illustrating a model configuration example of a noise cancellation
process of an internal model control FB scheme using the ear hole opening device according
to the embodiment.
FIG. 11 is a diagram illustrating a model configuration example of a noise cancellation
process using both the classical control FB scheme and the internal model control
FB scheme using the ear hole opening device according to the embodiment.
FIG. 12 is a diagram illustrating a model configuration example of a noise cancellation
process of the classical control FB scheme during music reproduction using the ear
hole opening device according to the embodiment.
FIG. 13 is a diagram illustrating a model configuration example of a noise cancellation
process of the classical control FB scheme including own voice extraction using the
ear hole opening device according to the embodiment.
FIG. 14 is a cross-sectional view illustrating a state of the inside of an ear canal
of user's left ear.
FIG. 15 is a view illustrating a state where the inside of the ear canal of user's
left ear illustrated in FIG. 14 is irradiated with a laser by the ear hole opening
device.
FIG. 16 is a view illustrating a state where the inside of the ear canal of user's
left ear illustrated in FIG. 14 is irradiated with a laser by the ear hole opening
device.
FIG. 17 is a view illustrating a state where the inside of the ear canal of user's
left ear illustrated in FIG. 14 is irradiated with a laser by the ear hole opening
device.
FIG. 18 is a diagram for describing a model configuration example of an eardrum sound
pressure estimation process according to the embodiment.
FIG. 19 is a view illustrating a state of scanning of the ear canal using the ear
hole opening device according to the embodiment.
FIG. 20 is a diagram for describing a model configuration example of the eardrum sound
pressure estimation process according to the embodiment.
FIG. 21 is a sequence diagram illustrating an example of flow of a personal authentication
process executed by the ear hole opening device and an external device according to
the embodiment.
FIG. 22 is a diagram for describing a technical problem of a second embodiment.
FIG. 23 is a diagram for describing a technical problem of the embodiment.
FIG. 24 is a graph for describing a technical problem of the embodiment.
FIG. 25 is a diagram for describing a technical problem of the embodiment.
FIG. 26 is a diagram for describing a technical problem of the embodiment.
FIG. 27 is a diagram for describing a technical problem of the embodiment.
FIG. 28 is a diagram for describing an example of an exterior configuration of headphones
according to the embodiment.
FIG. 29 is a view for describing an example of an exterior configuration of the headphones
according to the embodiment.
FIG. 30 is a view illustrating an example of a shape of a holding unit of the headphones
according to the embodiment.
FIG. 31 is a diagram illustrating an example of an internal configuration of the headphones
according to the embodiment.
FIG. 32 is a diagram illustrating a model configuration example of a first noise cancellation
process using the headphones according to the embodiment.
FIG. 33 is a diagram illustrating a model configuration example of a second noise
cancellation process using the headphones according to the embodiment.
FIG. 34 is a diagram illustrating a model configuration example of a secondary path
characteristic measurement process using the headphones according to the embodiment.
FIG. 35 is a diagram illustrating a model configuration example of a third noise cancellation
process using the headphones according to the embodiment.
FIG. 36 is a diagram illustrating a model configuration example of a fourth noise
cancellation process using the headphones according to the embodiment.
FIG. 37 is a diagram illustrating a model configuration example of a fifth noise cancellation
process using the headphones according to the embodiment.
FIG. 38 is a diagram for describing an example of a configuration of the headphones
according to the embodiment.
FIG. 39 is a diagram for describing an example of a configuration of the headphones
according to the embodiment.
FIG. 40 is a diagram for describing an example of a configuration of the headphones
according to the embodiment.
FIG. 41 is a view illustrating an example of a configuration of the holding unit of
the headphones according to the embodiment.
FIG. 42 is a view illustrating an example of a configuration of the holding unit of
the headphones according to the embodiment.
FIG. 43 is a view illustrating an example of a configuration of the holding unit of
the headphones according to the embodiment.
FIG. 44 is a view illustrating an example of a configuration of the holding unit of
the headphones according to the embodiment.
FIG. 45 is a view illustrating an example of a configuration of the holding unit of
the headphones according to the embodiment.
FIG. 46 is a view illustrating an example of a configuration of the holding unit of
the headphones according to the embodiment.
FIG. 47 is a diagram illustrating an example of a configuration of the headphones
according to the embodiment.
FIG. 48 is a view illustrating a configuration of the headphones illustrated in FIG.
47 as viewed from another viewpoint.
FIG. 49 is a view illustrating an example of a configuration of the headphones according
to the embodiment.
FIG. 50 is a diagram illustrating an example of a configuration of the headphones
according to the embodiment.
FIG. 51 is a view illustrating a configuration of the headphones illustrated in FIG.
50 as viewed from another viewpoint.
FIG. 52 is a view illustrating a configuration of the headphones illustrated in FIG.
50 as viewed from another viewpoint.
FIG. 53 is a view illustrating a configuration of the headphones illustrated in FIG.
50 as viewed from another viewpoint.
FIG. 54 is a diagram illustrating a configuration when the headphones illustrated
in FIG. 50 are not worn.
FIG. 55 is a diagram illustrating an example of a configuration of headphones according
to the embodiment.
FIG. 56 is a diagram illustrating an example of a configuration of the headphones
according to the embodiment.
FIG. 57 is a view illustrating a configuration of the headphones illustrated in FIG.
56 as viewed from another viewpoint.
FIG. 58 is a view illustrating a configuration of the headphones illustrated in FIG.
56 as viewed from another viewpoint.
FIG. 59 is a view illustrating a configuration of the headphones illustrated in FIG.
56 as viewed from another viewpoint.
FIG. 60 is a diagram illustrating an example of a configuration of the headphones
according to the embodiment.
FIG. 61 is a view illustrating a configuration of the headphones illustrated in FIG.
60 as viewed from another viewpoint.
FIG. 62 is a view illustrating an example of a configuration of the headphones according
to the embodiment.
FIG. 63 is a view illustrating an example of a configuration of the headphones according
to the embodiment.
FIG. 64 is a diagram illustrating an example of a configuration of the headphones
according to the embodiment.
FIG. 65 is a diagram illustrating an example of an internal configuration of an ear
hole opening device according to a third embodiment.
FIG. 66 is a diagram for describing an outline of the ear hole opening device according
to the embodiment.
FIG. 67 is a diagram illustrating an example of the internal configuration of headphones
according to the embodiment.
FIG. 68 is a diagram for describing the outline of the ear hole opening device according
to the embodiment.
FIG. 69 is a diagram for describing a first combination example of the ear hole opening
device and the headphones according to the embodiment.
FIG. 70 is a diagram for describing a second combination example of the ear hole opening
device and the headphones according to the embodiment.
FIG. 71 is a diagram for describing a third combination example of the ear hole opening
device and the headphones according to the embodiment.
FIG. 72 is a diagram for describing a fourth combination example of the ear hole opening
device and the headphones according to the embodiment.
FIG. 73 is a diagram for describing a fifth combination example of the ear hole opening
device and the headphones according to the embodiment.
FIG. 74 is a diagram for describing a sixth combination example of the ear hole opening
device and the headphones according to the embodiment.
FIG. 75 is a diagram for describing an example of wireless communication processing
using light between the ear hole opening device and headphones according to the embodiment.
FIG. 76 is a diagram for describing an example of the wireless communication processing
using light between the ear hole opening device and headphones according to the embodiment.
FIG. 77 is a diagram for describing an example of the wireless communication processing
using light between the ear hole opening device and headphones according to the embodiment.
FIG. 78 is a diagram for describing an example of wireless communication processing
using NFMI between the ear hole opening device and headphones according to the embodiment.
FIG. 79 is a view for describing mutual device detection using an RFID device performed
by the ear hole opening device and the headphones according to the embodiment.
FIG. 80 is a sequence diagram illustrating an example of processing flow when a noise
cancellation process according to the embodiment is started based on contactless power
supply from the headphones to the ear hole opening device.
FIG. 81 is a sequence diagram illustrating an example of processing flow when the
noise cancellation process according to the embodiment is started based on contactless
power supply from the ear hole opening device to the headphones.
FIG. 82 is a view for describing the mutual device detection using NFMI performed
by the ear hole opening devices and the headphones according to the embodiment.
FIG. 83 is a view for describing the mutual device detection using NFMI performed
by the ear hole opening devices and the headphones according to the embodiment.
FIG. 84 is a view for describing the mutual device detection using NFMI performed
by the ear hole opening devices and the headphones according to the embodiment.
FIG. 85 is a view for describing the mutual device detection using NFMI performed
by the ear hole opening devices and the headphones according to the embodiment.
FIG. 86 is a sequence diagram illustrating an example of processing flow when the
noise cancellation process according to the embodiment is started based on magnetic
resonance among the ear hole opening devices and the headphones.
FIG. 87 is a diagram for describing mutual device detection using audio by the ear
hole opening device and the headphones according to the embodiment.
FIG. 88 is a diagram for describing mutual device detection using magnetism by the
ear hole opening device and the headphones according to the embodiment.
FIG. 89 is a block diagram illustrating an example of a hardware configuration of
an information processing apparatus according to each embodiment.
Description of Embodiments
[0011] Hereinafter, preferred embodiments of the present disclosure will be described in
detail with reference to the accompanying drawings. Note that constituent elements
having substantially the same functional configuration in the present specification
and the drawings will be denoted by the same reference sign, and the redundant description
thereof will be omitted.
[0012] Note that a description will be given in the following order.
- 1. First embodiment
- 2. Second embodiment
- 3. Third embodiment
- 4. Hardware Configuration Example
- 5. Summary
<<1. First Embodiment>>
[0013] The present embodiment relates to a noise cancellation process using an audio processing
device (ear hole opening device) having an audio information acquisition unit arranged
near an entrance of an ear canal.
<1.1. Technical Problem>
[0014] In recent years, various wearable devices that are assumed to be constantly worn
have been developed. For example, an ear hole opening device that does not seal an
ear hole (an entrance of the ear canal) in a worn state has appeared in recent years.
The ear hole opening device is a kind of so-called earphone device, and is used by
being worn by a user similarly to the earphone device. However, the ear hole opening
device does not seal the ear hole in the worn state, and thus, achieves listening
characteristics of ambient sounds equivalent to that in a non-wearing state. However,
an ear is not sealed with an ear pad or the like in the ear hole opening device, and
thus, it is difficult to expect noise cancellation due to passive sound insulation.
Therefore, it is desirable to add a noise cancellation function by active processing
to the ear hole opening device. However, the above-described Patent Literatures 1
and 2 only disclose a noise cancellation process in sealed earphones/headphones.
[0015] Therefore, the present embodiment discloses a no-noise cancellation process based
on active processing suitable for an ear hole opening type device.
<1.2. Exterior Configuration of Ear Hole Opening Device>
[0016] FIG. 1 is a view for describing an example of an exterior configuration of the ear
hole opening device according to the present embodiment. As illustrated in FIG. 1,
an ear hole opening device 100 is used by being worn on one ear of a listener (that
is, a user). FIG. 1 illustrates the exterior of the ear hole opening device 100 worn
on a right ear as an example. The Y axis is a coordinate axis with the front in the
horizontal direction (eye direction) as positive, the X axis is a coordinate axis
with the left side of a person in the horizontal direction as positive, and the Z
axis is a coordinate axis with the vertical direction as negative. These coordinate
axes are also used in the subsequent drawings.
[0017] As illustrated in FIG. 1, the ear hole opening device 100 includes: an audio output
unit 110 that outputs (generates) audio; a sound guide unit 120 that takes audio generated
by the audio output unit 110 from one end 121; and a holding unit 130 that holds the
sound guide unit 120 near another end 122. The sound guide unit 120 is made of a hollow
tube material, and both ends thereof are open ends. The one end 121 of the sound guide
unit 120 is an audio input hole for a sound generated from the audio output unit 110,
and the other end 122 is an audio output hole. Therefore, the sound guide unit 120
is in the state of being open on one side as the one end 121 is attached to the audio
output unit 110.
[0018] The holding unit 130 is engaged with the vicinity of the entrance of the ear canal
(for example, an intertragic notch) to support the sound guide unit 120 near the other
end 122 such that the audio output hole of the other end 122 of the sound guide unit
120 faces the interior side of the ear canal. An outer diameter of the sound guide
unit 120 at least near the other end 122 is formed to be smaller than an inner diameter
of the ear hole (entrance of an ear canal 5). Therefore, the ear hole of the listener
is not blocked even in a state where the other end 122 of the sound guide unit 120
is held near the entrance of the ear canal by the holding unit 130. That is, the ear
hole is open. It is possible to say that the ear hole opening device 100 is different
from a typical earphone and is an ear hole opening type earphone.
[0019] In addition, the holding unit 130 includes an opening portion 131 that opens the
ear hole to the outside even in the state of holding the sound guide unit 120. In
the example illustrated in FIG. 1, the holding unit 130 is a ring-shaped structure,
an audio information acquisition unit 140 is provided in a part where rod-shaped support
members 132 provided in a ring inner direction are combined near the ring center,
and all the other parts of the ring-shaped structure are the opening portions 131.
Note that the holding unit 130 is not limited to the ring-shaped structure but may
have an arbitrary shape that supports the other end 122 of the sound guide unit 120
and is provided with the audio information acquisition unit 140 as long as a hollow
structure is provided.
[0020] When taking the audio generated by the audio output unit 110 into the tube from the
one end 121 thereof, the tubular sound guide unit 120 propagates the air vibration
thereof to be radiated from the other end 122 held near the entrance of the ear canal
by the holding unit 130 toward the ear canal and transmitted to an eardrum.
[0021] As described above, the holding unit 130 holding the vicinity of the other end 122
of the sound guide unit 120 includes the opening portion 131 that opens the entrance
(ear hole) of the ear canal to the outside. Therefore, the ear hole of the listener
is not blocked even in the state where the ear hole opening device 100 is worn. The
listener can sufficiently listen to ambient sounds through the opening portion 131
in the middle of wearing the ear hole opening device 100 and listening to the audio
output from the audio output unit 110.
[0022] In addition, although the ear hole opening device 100 according to the present embodiment
opens the ear hole, the leakage of the sound generated from the audio output unit
110 (that is, the reproduced sound) to the outside can be reduced. This is because
the other end 122 of the sound guide unit 120 is attached so as to face the interior
of the ear canal near the entrance of the ear canal and sufficient sound quality can
be obtained even if the output of the audio output unit 110 is small. In addition,
the directivity of the air vibration radiated from the other end 122 of the sound
guide unit 120 can also contribute to prevention of the sound leakage.
[0023] The sound guide unit 120 has a bent shape that is folded back from the back side
of a pinna to the front side at a middle part. This bent part forms a pinch portion
123 having an opening and closing structure, and can maintain the ear hole opening
device 100 worn by the listener by generating a pinching force to pinch an earlobe.
[0024] The audio information acquisition unit 140 provided near the ring center of the ring-shaped
holding unit 130 is provided to face the opposite side of the eardrum. The audio information
acquisition unit 140 typically includes an audio input unit (that is, a microphone)
and mainly detects (that is, collects) ambient sounds. That is, the audio input unit
is provided in the opposite direction to the other end 122 arranged to face the interior
side of the ear canal. Therefore, the influence of the sound generated from the audio
output unit 110 output from the other end 122 on a sound collection result by the
audio input unit is mitigated.
[0025] The audio information acquisition unit 140 functions as a so-called error microphone
for noise cancellation, and a detection result by the audio information acquisition
unit 140 is treated as an error signal. Since the audio information acquisition unit
140 is arranged near the ear hole, that is, near the eardrum, high noise canceling
performance is expected.
[0026] Note that the ear hole opening device 100 illustrated in FIG. 1 is configured assuming
wearing on the right ear, but the ear hole opening device 100 for wearing on the left
ear is configured to be laterally symmetric with respect to this configuration. In
addition, the ear hole opening device 100 may be configured for both ears including
both the right ear and the left ear. In the case of being configured for both ears,
the ear hole opening device 100 for the right ear and the ear hole opening device
100 for the left ear may be configured separately to be independent from each other
and communicate with each other.
<1.3. Internal Configuration of Ear Hole Opening Device>
[0027] FIG. 2 is a diagram illustrating an example of an internal configuration of the ear
hole opening device 100 according to the present embodiment. As illustrated in FIG.
2, the ear hole opening device 100 includes the audio output unit 110, the audio information
acquisition unit 140, and a control unit 150.
• Audio Output Unit 110
[0028] The audio output unit 110 has a function of outputting audio based on an audio signal.
The audio output unit 110 can also be referred to as a driver. The driver 110 outputs
audio to a space based on an output signal output from a signal processing unit 151.
• Audio Information Acquisition Unit 140
[0029] The audio information acquisition unit 140 has a function of acquiring audio information.
The audio information acquisition unit 140 includes an audio input unit 141 and an
eardrum sound pressure acquisition unit 142.
[0030] The audio input unit 141 includes a microphone (hereinafter also simply referred
to as a microphone) that detects ambient sounds and generates an audio signal indicating
the sound collection result by the microphone. That is, the audio information may
be the audio signal indicating the sound collection result by the microphone. The
eardrum sound pressure acquisition unit 142 estimates a sound pressure of the eardrum
and generates sound pressure information of the eardrum. That is, the audio information
may be the eardrum sound pressure information. The eardrum sound pressure acquisition
unit 142 directly estimates the eardrum sound pressure, for example, by measuring
a vibration of the eardrum. A configuration of the eardrum sound pressure acquisition
unit 142 will be described in detail later.
[0031] Note that the eardrum sound pressure does not need to be measured directly. For example,
the eardrum sound pressure may be approximated with a sound pressure near the entrance
of the ear canal. Since the audio input unit 141 (audio information acquisition unit
140) is held near the entrance of the ear canal as illustrated in FIG. 1, the audio
signal generated by the audio input unit 141 can also be grasped as information indicating
the eardrum sound pressure.
• Control Unit 150
[0032] The control unit 150 functions as an arithmetic processing device and a control device,
and controls the entire processing performed by the ear hole opening device 100 according
to various programs. The control unit 150 is realized by an electronic circuit, for
example, a central processing unit (CPU), a micro-processing unit (MPU), a demand-side
platform (DSP), or the like. Note that the control unit 150 may include a read-only
memory (ROM) that stores programs to be used, calculation parameters, and the like,
and a random-access memory (RAM) that temporarily stores parameters that change as
appropriate.
[0033] As illustrated in FIG. 2, the control unit 150 includes the signal processing unit
151, an operation control unit 153, and an authentication unit 155.
[0034] The signal processing unit 151 has a function of generating a noise cancellation
signal for noise based on the audio information (audio signal or eardrum sound pressure
information) acquired by the audio information acquisition unit 140. For example,
the signal processing unit 151 performs a noise cancellation process of a FB scheme
or a FF scheme using the audio information as an error signal to generate the noise
cancellation signal. The signal processing unit 151 generates an audio signal (hereinafter
also referred to as an output signal) based on the noise cancellation signal, and
outputs the audio signal to the audio output unit 110 as an output. The output signal
may be the noise cancellation signal itself or may be a synthesized signal obtained
by synthesizing another audio signal such as a music signal acquired from a sound
source and the noise cancellation signal. The signal processing unit 151 includes
various constituent elements for noise cancellation processes which will be described
with reference to FIGS. 8 to 13 and the like. For example, the signal processing unit
151 includes: various filter circuits configured to generate a noise cancellation
signal; an adaptive control unit configured to adaptively control the filter circuits;
an adder configured to synthesize signals; an own voice extraction unit to be described
later; an internal model; and the like. In addition, the signal processing unit 151
also includes circuits such as an amplifier, an analog-digital converter (ADC), and
a digital-analog converter (DAC). The signal processing unit 151 may perform not only
the noise cancellation process but also a process of emphasizing a high range of sound
information included in the audio information (audio signal or eardrum sound pressure
information) acquired by the audio information acquisition unit 140, adding a reverberation,
or the like. As a result, it is possible to make it easy to hear ambient sounds. That
is, the technique according to the present embodiment can be also applied to a noise
cancellation technique in an open space or a hearing aid.
[0035] The operation control unit 153 has a function of controlling an operation mode of
the ear hole opening device 100. For example, the operation control unit 153 stops
or starts some or all of the functions of the ear hole opening device 100.
[0036] The authentication unit 155 has a function of identifying and authenticating a user
wearing the ear hole opening device 100.
<1.4. Wearing Mode of Ear Hole Opening Device>
[0037] FIG. 3 is a view for describing an outline of the noise cancellation process using
the ear hole opening device 100 according to the present embodiment. FIG. 3 illustrates
a cross-sectional view at the ear canal of the head of the user wearing the ear hole
opening device 100 on the left ear. As illustrated in FIG. 3, noise N reaches the
audio information acquisition unit 140, passes through the opening portion 131, and
passes through the ear canal 5 to reach an eardrum 9. The ear hole opening device
100 generates a noise cancellation signal based on the noise N acquired by the audio
information acquisition unit 140. The audio output unit 110 outputs audio based on
an audio signal generated based on the noise cancellation signal. The audio output
from the audio output unit 110 propagates through the sound guide unit 120 and is
released from the other end 122 to cancel the noise N.
[0038] As illustrated in FIG. 3, a position of the audio information acquisition unit 140
is near the entrance of the ear canal 5, that is, near the eardrum 9. For this reason,
the microphone 141 can collect the audio near the eardrum 9. When a noise cancellation
process is performed using the microphone 141 as a cancellation point, high noise
canceling performance is realized. In addition, the eardrum sound pressure acquisition
unit 142 can acquire sound pressure information of the eardrum 9 from the vicinity
of the eardrum 9. As a result, the precision of sound pressure information increases,
which can contribute to the improvement of noise canceling performance.
[0039] The holding unit 130 maintains a relative positional relationship between the audio
information acquisition unit 140 and the other end 122 that is the output hole of
the audio output from the audio output unit 110. That is, a characteristic (characteristic
H
1 to be described later) of a space between the audio output unit 110 and the audio
information acquisition unit 140 is fixed. As a result, the noise canceling performance
can be stabilized. Note that the relative positional relationship is maintained by
the holding unit 130 holding both the sound guide unit 120 and the audio information
acquisition unit 140 together.
[0040] Next, a wearing position of the ear hole opening device will be described with reference
to FIGS. 4 to 7. Hereinafter, a description will be given assuming that the ear hole
opening device 100 is equipped with the microphone 141 as the audio information acquisition
unit 140.
[0041] FIG. 4 is a view for describing a typical human ear structure. As illustrated in
FIG. 4, a pinna 2 forms specific unevenness in a human ear 1 and reflects audio from
various directions to guide the reflected audio to the ear canal 5. The ear canal
5 is a passage of audio, and the audio that has passed through the ear canal 5 reaches
the eardrum at the interior of the ear canal 5. Around the ear canal 5, there are
a crus of helix 3, a cavum concha 4, a tragus 6, an intertragic notch 7, and an antitragus
8.
[0042] FIG. 5 is a view for describing the noise N arriving at the human ear. As illustrated
in FIG. 5, the noise N arrives at the human ear 1 from all directions in a horizontal
direction. Although FIG. 5 illustrates the left ear, the same applies to the right
ear. Noise collected by the microphone 141 has a frequency characteristic that depends
on an arrival direction of the noise depending on the arrangement of the microphone
141. For example, the influence of reflection received from the pinna 2 differs between
noise coming from the front of the user (that is, the Y-axis positive side) and noise
coming from the back (that is, the Y-axis negative side). Therefore, even if noise
from a specific direction can be canceled sufficiently, there may occur an event where
it is difficult to sufficiently noise from another direction depending on the arrangement
of the microphone 141 This is not limited to the horizontal direction, and the same
applies to an elevation direction.
[0043] FIG. 6 is a view for describing the arrangement of the microphone 141 of the ear
hole opening device 100 according to the present embodiment. FIG. 6 illustrates a
cross-sectional view illustrating a state of the ear canal. As illustrated in FIG.
6, the ear canal 5 has an S-shape bending at each of a first curve 11 and a second
curve 12, and the eardrum 9 is located at the interior of the ear canal 5. It is considered
that the dependence of the frequency characteristic on the noise arrival direction
described above with reference to FIG. 5 is relatively small if a space closer to
the eardrum 9 than the tragus 6. Therefore, it is desirable that the microphone 141
be arranged in the space closer to the eardrum 9 than the tragus 6. More specifically,
it is desirable that the microphone 141 be arranged inside the ear canal 5, that is,
in the space closer to the eardrum 9 than a boundary 19 between the cavum concha 4
and the ear canal 5. As a result, the particularly high noise canceling performance
can be realized.
[0044] It is desirable that the microphone 141 be arranged in a space 15 mm away from the
boundary 19 of the cavum concha 4 and the ear canal 5 to the eardrum 9 side or arranged
in a space 15 mm away from the boundary 19 of the cavum concha 4 and the ear canal
5 on the opposite side of the eardrum 9. In other words, it is desirable that the
holding unit 130 hold the microphone 141 in the space 15 mm away from the boundary
19 of the cavum concha 4 and the ear canal 5 to the eardrum 9 side or in the space
15 mm away from the boundary 19 of the cavum concha 4 and the ear canal 5 on the opposite
side of the eardrum 9 in a state where the ear hole opening device 100 is worn by
the user. Here, a difference between the frequency characteristic at the position
of the microphone 141 and the frequency characteristic at the position of the eardrum
9 decreases as the microphone 141 approaches the eardrum 9. Therefore, it is more
desirable if the position of the microphone 141 is closer to the eardrum 9. In this
regard, the above difference between the frequency characteristics can fall within
an allowable range if the space 15 mm away from the boundary 19 to the opposite side
of the eardrum 9, and the predetermined noise canceling performance can be ensured.
In addition, in the case where the microphone 141 is arranged in the range within
15 mm away from the boundary 19 to the eardrum 9 side, the position of the microphone
141 can be made closer to the eardrum 9 as compared with the case where the microphone
141 is arranged in the space away from the boundary 19 on the opposite side of the
eardrum 9. Further, at least the microphone 141 can be prevented from coming into
contact with the eardrum 9 and damaging the eardrum 9, and the safety can be ensured.
[0045] Microphone positions M-a and M-b are in the space 15 mm away from the boundary 19
to the eardrum 9 side. Specifically, the microphone position M-a is between the first
curve 11 and the second curve 12 of the ear canal 5. The microphone position M-b is
between the boundary 19 and the first curve 11 of the ear canal 5. In addition, a
microphone position M-c is in the space 15 mm away from the boundary 19 on the opposite
side of the eardrum 9. The predetermined noise canceling performance can be ensured
at any of these microphone positions. In particular, the microphone position M-a is
most desirable in terms that the dependence of the frequency characteristics on the
arrival direction can be minimized.
[0046] FIG. 7 is a view illustrating a state where the ear hole opening device 100 according
to the present embodiment is worn by the user. As illustrated in FIG. 7, the holding
unit 130 abuts on an inner wall of the ear canal 5 of one ear in the state where the
ear hole opening device 100 is worn by the user. Then, the holding unit 130 holds
the microphone 141 in the space closer to the eardrum 9 than the tragus 6, the space
15 mm away from the boundary 19 between the cavum concha 4 and the ear canal 5 to
the eardrum 9 side. More specifically, the holding unit 130 holds the microphone 141
at the microphone position M-a illustrated in FIG. 6. With such an arrangement, the
position of the microphone 141 (that is, the cancellation point) can be set to a position
where the difference in frequency characteristics from the position of the eardrum
9 is small, and the high noise canceling performance can be realized. Note that a
place where the holding unit 130 abuts is not limited to the inner wall of the ear
canal 5. The holding unit 130 may abut on the cavum concha 4, for example.
<1.5. Details of Noise Cancellation Process>
[0047] Hereinafter, the noise cancellation process using the ear hole opening device 100
according to the present embodiment will be described.
(1) Classical Control FB Scheme
[0048] First, a classical control FB scheme will be described with reference to FIGS. 8
and 9.
[0049] FIG. 8 is a diagram illustrating a model configuration example of the noise cancellation
process of the classical control FB scheme using the ear hole opening device 100 according
to the present embodiment. Symbols of blocks illustrated in the model configuration
example as illustrated in FIG. 8 indicate characteristics (that is, transfer functions)
corresponding to specific circuit parts, circuit systems in a noise cancellation system,
or the like. Each time an audio signal (or audio) passes through each block, the characteristic
illustrated in the corresponding block is applied. The symbols in the blocks illustrated
in FIGS. 8 to 13 have meanings as follows.
H1: Characteristic of space 203 from driver 110 to microphone 141
H2: Characteristic of space 205 from microphone 141 to eardrum (spatial characteristic
of ear canal)
M: Characteristic of microphone 141
A: Characteristic of amplifier 202
D: Characteristic of driver 110
F: Characteristic of passive sound insulation element 220
M': Simulated characteristic of M of microphone 141
A': Simulated characteristic of amplifier 202
D': Simulated characteristic of driver 110
H': Simulated characteristic of space 203
A'D'H1'M': Characteristic of internal model 208
-β1: Characteristic of first FB filter 201
β2: Characteristic of second FB filter 207
E: Characteristic of equalizer 213
[0050] In addition, N represents noise, M represents a music signal, P represents a sound
pressure at an eardrum position, and V represents user's voice (own voice).
[0051] The microphone 141 collects audio and generates an audio signal. The audio signal
generated by the microphone 141 is input to the first FB filter 201.
[0052] The first FB filter 201 is a filter circuit that performs the noise cancellation
process of the FB scheme. The first FB filter 201 performs the noise cancellation
process using the microphone 141 as the cancellation point based on the audio signal
input from the microphone 141, and generates a noise cancellation signal. The audio
signal that has passed through the first FB filter 201 is input to the amplifier 202.
[0053] The amplifier 202 is a power amplifier that amplifies and outputs the input audio
signal. The amplifier 202 amplifies and outputs the audio signal input from the first
FB filter 201. The audio signal that has passed through the amplifier 202 is input
to the driver 110.
[0054] The driver 110 outputs audio inside a space based on the input audio signal.
[0055] The audio output from the driver 110 first passes through the space 203 and then
interferes with the noise N in a space 204 to cancel the noise N. The noise N that
has not been canceled is collected by the microphone 141. Further, the noise N that
has not been canceled passes through the opening portion 131, passes through the space
205, and reaches the eardrum position as the eardrum sound pressure P.
[0056] The microphone 141 is a point that minimizes noise (that is, the cancellation point).
Therefore, it is desirable if the arrangement position of the microphone 141 is closer
to the eardrum.
[0057] Here, as a comparative example, a noise cancellation process in a case where the
ear hole opening device 100 is configured as an earphone (sealed noise canceling earphone)
that does not have the opening portion 131 will be described with reference to FIG.
9.
[0058] FIG. 9 is a diagram illustrating a model configuration example of the noise cancellation
process of the classical control FB scheme using the sealed noise canceling earphone
according to the comparative example. The model configuration example illustrated
in FIG. 9 is the same as the model configuration example illustrated in FIG. 8 except
that the passive sound insulation element 220 is provided. In the sealed noise canceling
earphone, the passive sound insulation element 220, such as a sealed housing and an
earpiece, is present between the noise N and the microphone 141. For this reason,
the noise N is attenuated by the influence of the passive sound insulation element
220 and then collected by the microphone 141. In other words, relatively large noise
is collected in the ear hole opening device 100 as compared with the sealed noise
canceling earphone. Therefore, it is desirable that the ear hole opening device 100
according to the present embodiment use an amplifier and a driver that have a larger
output than the sealed noise canceling earphone.
[0059] Here, the noise cancellation process of the classical control FB scheme using the
ear hole opening device 100, which has been described with reference to FIG. 8, will
be considered.
[0060] First, the audio signal input to the driver 110 is defined as y. Then, the sound
pressure P at the position of the microphone 141 is defined by the following Formula
(A1).
[0061] The audio signal y is defined by the following Formula (A2).
[0062] The sound pressure P is derived by the following Formula (A3) from the Formulas (A1)
and (A2).
[0063] Here, a coefficient relating to the noise N in Formula (A3) will be also referred
to as a sensitivity function. A characteristic β
1 of the first FB filter 201 is a designable parameter. As β
1 is maximized, the denominator of the sensitivity coefficient is maximized, the sensitivity
coefficient is minimized, so that the sound pressure P is minimized. That is, as β
1 is maximized, the sound pressure at the eardrum position decreases, and noise is
canceled more greatly.
(2) Internal Model Control FB Scheme
[0064] Next, an internal model control FB scheme (inter model control (IMC) scheme) will
be described with reference to FIG. 10.
[0065] FIG. 10 is a diagram illustrating a model configuration example of a noise cancellation
process of the internal model control FB scheme using the ear hole opening device
100 according to the present embodiment. The model configuration example illustrated
in FIG. 10 is different from the model configuration example illustrated in FIG. 8
in terms that the second FB filter 207 is provided instead of the first FB filter
201 and the internal model 208 and an adder 206 are provided. Hereinafter, differences
from the model configuration example illustrated in FIG. 8 will be mainly described.
[0066] The second FB filter 207 is a filter circuit that performs the noise cancellation
process of the FB scheme. The second FB filter 207 performs the noise cancellation
process using the microphone 141 as the cancellation point based on the input audio
signal, and generates a noise cancellation signal. The audio signal that has passed
through the second FB filter 207 is input to the amplifier 202 and also input to the
internal model 208.
[0067] The internal model 208 corresponds to the internal model of the ear hole opening
device 100. The internal model is a signal processing internal path, and is a model
having a characteristic simulating a secondary path. Note that the secondary path
is a physical space transfer characteristic from a secondary sound source to an error
microphone. The internal model 208 herein has characteristics simulating characteristics
until the noise cancellation signal output from the second FB filter 207 is output
from the driver 110 and collected by the microphone 141 and returns to the second
FB filter. The internal model 208 in the model configuration example illustrated in
FIG. 10 has a characteristic of A'D'H
1'M'. The audio signal that has passed through the internal model 208 is input to the
adder 206. The adder 206 subtracts the audio signal that has passed through the internal
model 208 from the audio signal generated by the microphone 141 to perform synthesis.
The synthesized signal is input to the second FB filter 207.
(3) Combination of Classical Control FB Scheme and Internal Model Control FB Scheme
[0068] Next, a case where the classical control FB scheme and the internal model control
FB scheme are used in combination will be described with reference to FIG. 11.
[0069] FIG. 11 is a diagram illustrating a model configuration example of a noise cancellation
process using both the classical control FB scheme and the internal model control
FB scheme using the ear hole opening device 100 according to the present embodiment.
The model configuration example illustrated in FIG. 11 is obtained by adding a first
FB filter (characteristic: -β
1) and an adder 209 to the model configuration example illustrated in FIG. 10. Hereinafter,
constituent elements newly added to the model configuration example illustrated in
FIG. 10 will be mainly described.
[0070] The audio signal input from the microphone 141 is input to the adder 206 and also
input to the first FB filter 201. As described above, the first FB filter 201 generates
the noise cancellation signal based on the input audio signal.
[0071] The audio signals that have passed through each of the first FB filter 201 and the
second FB filter 207 are input to the adder 209 to be synthesized. The synthesized
signal is input to the internal model 208 and output from the driver 110 via the amplifier
202.
[0072] Although the noise cancellation process of the FB scheme has been described as above,
the present technique is not limited to this example. The ear hole opening device
100 may perform noise cancellation process of the FF scheme together with or instead
of the noise cancellation process of the FB scheme. In such a case, it is desirable
that the ear hole opening device 100 measure audio characteristics when being worn
by the user in advance and sets the characteristics of the FF filter.
(4) Processing in Music Reproduction
[0073] FIG. 12 is a diagram illustrating a model configuration example of a noise cancellation
process of the classical control FB scheme during music reproduction using the ear
hole opening device 100 according to the present embodiment. In the model configuration
example illustrated in FIG. 12, an internal model 208, an adder 210, and an adder
211 are added to the model configuration example illustrated in FIG. 8, and an audio
signal M is additionally input. Hereinafter, constituent elements newly added to the
model configuration example illustrated in FIG. 8 will be mainly described.
[0074] The music signal M is input to the internal model 208 and the adder 211. The music
signal that has passed through the internal model 208 is input to the adder 210. In
addition, the audio signal generated by the microphone 141 is input to the adder 210.
The adder 210 subtracts the music signal that has passed through the internal model
208 from the audio signal generated by the microphone 141 to perform synthesis. Then,
the synthesized signal is input to the first FB filter 201. The audio signal that
has passed through the first FB filter 201 is input to the adder 211. The adder 211
synthesizes the audio signal that has passed through the first FB filter 201 and the
music signal M. The synthesized signal is output from the driver 110 via the amplifier
202.
[0075] In this manner, the FB filter is applied after subtracting the music signal component
from the noise-containing audio signal output from the microphone 141 in this noise
cancellation process. As a result, it is possible to prevent music that needs to be
reproduced from being reduced together with noise.
(5) Processing in Own Voice Extraction
[0076] The signal processing unit 151 extracts user's own voice based on the audio information
acquired by each of the pair of audio information acquisition units 140 for both ears,
and synthesizes the extracted user's voice with the noise cancellation signal. When
noise is collected including the user's own voice, the noise cancellation signal includes
a component that cancels the user's own voice. In this regard, the user's own voice
is output at the ear as the user's own voice is synthesized with the noise cancellation
signal. Accordingly, it is possible to prevent the user from feeling uncomfortable
as if his/her voice is canceled as noise and his/her voice becomes distant. Hereinafter,
a process of extracting the own voice and synthesizing the extracted voice with the
noise cancellation signal will be described in detail with reference to FIG. 13.
[0077] FIG. 13 is a diagram illustrating a model configuration example of a noise cancellation
process of the classical control FB scheme including own voice extraction using the
ear hole opening device 100 according to the present embodiment. The model configuration
example illustrated in FIG. 13 is obtained by adding an own voice extraction unit
212, an equalizer 213, an adder 214, and a space 215 to the model configuration example
illustrated in FIG. 8. The incoming noise N is audio obtained by synthesizing a noise
source NS and user's speech voice V (that is, own voice) in the space 215. However,
the model configuration example illustrated in FIG. 13 illustrates the model configuration
example on the left ear side, and does not illustrate the right ear side. Hereinafter,
constituent elements newly added to the model configuration example illustrated in
FIG. 8 will be mainly described in the model configuration example illustrated in
FIG. 13.
[0078] The microphone 141 for the left ear collects the noise N having passed through the
space 204 and generates an audio signal. The same applies to the right ear. The audio
signals generated by the left and right microphones 141 are input to the own voice
extraction unit 212. The own voice extraction unit 212 extracts the own voice V based
on the input audio signals. For example, the own voice extraction unit 212 extracts
the own voice V by extracting an in-phase signal component from the input audio signal.
The own voice extraction unit 212 outputs an audio signal indicating the extracted
own voice V to the left and right adders 214.
[0079] Meanwhile, the audio signal generated by the microphone 141 is also input to the
first FB filter 201. A noise cancellation signal generated by the first FB filter
201 is input to the adder 214. In addition, the music signal M is input to the equalizer
213. The equalizer 213 adjusts the sound quality of the input music signal M based
on the characteristic E. The music signal that has passed through the equalizer 213
is input to the adder 214.
[0080] The adder 214 synthesizes the audio signals input from each of the own voice extraction
unit 212, the first FB filter 201, and the equalizer 213. The synthesized signal is
output from the driver 110 via the amplifier 202.
[0081] As a result, even if the own voice V having passed through the opening portion 131
is canceled by the noise cancellation signal, the own voice V extracted by the own
voice extraction unit 212 is output from the driver 110. As a result, it is possible
to prevent the user from feeling uncomfortable as if his/her voice is canceled as
noise and his/her voice becomes distant.
[0082] Note that the ear hole opening device 100 may further include a microphone configured
to collect user's own voice as the audio information acquisition unit 140 in addition
to the microphone 141 held by the holding unit 130. For example, the ear hole opening
device 100 can include the microphone in the vicinity of the pinch portion 123 illustrated
in FIG. 1. In such a case, the own voice extraction unit 212 extracts the user's voice
based on an audio signal generated by the microphone. As a result, the own voice extraction
unit 212 can extract the user's voice with higher accuracy.
<1.6. Noise Cancellation Process Based on Sound Pressure Information of Eardrum>
[0083] The ear hole opening device 100 may perform a noise cancellation process based on
eardrum sound pressure information. In such a case, the audio information acquisition
unit 140 acquires the eardrum sound pressure information as audio information. Then,
the signal processing unit 151 performs the noise cancellation process based on the
eardrum sound pressure information instead of the audio signal generated by the microphone
141. Of course, the signal processing unit 151 may perform the noise cancellation
process using both the audio signal generated by the microphone 141 and the eardrum
sound pressure information acquired by the eardrum sound pressure acquisition unit
142. Hereinafter, a description will be given assuming that the ear hole opening device
100 is equipped with the eardrum sound pressure acquisition unit 142 as the audio
information acquisition unit 140.
(1) Configuration of Eardrum Sound Pressure Acquisition Unit 142
[0084] The eardrum sound pressure acquisition unit 142 has a function of acquiring vibration
information of the ear canal or the eardrum and acquiring sound pressure information
of a cancellation point based on the acquired vibration information.
[0085] Specifically, the eardrum sound pressure acquisition unit 142 transmits a transmission
wave, acquires a reflection wave which is the reflected transmission wave, and acquires
the vibration information indicating displacement or speed at a reflection point.
In the reflection wave, a frequency change proportional to a movement speed of the
reflection point occurs. Specifically, a frequency of the reflection wave increases
when an object approaches, and the frequency decreases when the object moves away.
The eardrum sound pressure acquisition unit 142 estimates the displacement or speed
of the reflection point based on a frequency difference between the transmission wave
and the reflection wave. The transmission wave is transmitted to the ear canal or
the eardrum, and is reflected at an arbitrary reflection point in the ear canal or
the eardrum. The reflection point may be the same as or different from the cancellation
point.
[0086] For example, the eardrum sound pressure acquisition unit 142 may be realized by a
laser distance measuring device, and the transmission wave may be a laser. In addition,
the eardrum sound pressure acquisition unit 142 may be realized by an ultrasonic distance
measuring device, and in this case, the transmission wave is an ultrasonic wave. However,
the transmission wave is desirably a laser from the viewpoint of interference. In
the case of using the laser, there is an advantage that collection of wind noise by
the microphone 141 does not occur in principle. Note that a laser light source may
emit light intermittently instead of emitting light continuously. In addition, the
light emission frequency may be equal to a sampling rate relating to reflection wave
acquisition. As a result, power consumption can be reduced. Hereinafter, a description
will be given assuming that the eardrum sound pressure acquisition unit 142 is realized
by the laser distance measuring device.
[0087] The eardrum sound pressure acquisition unit 142 can also measure a distance between
the eardrum sound pressure acquisition unit 142 and the reflection point. For example,
the laser distance measuring device measures a distance between the laser distance
measuring device and the reflection point based on a time from transmission of a laser
to reception of the laser reflected from the reflection point. Such a measurement
method will be also referred to as a time of flight (ToF) scheme. Note that it is
sufficient that at least a device that transmits a transmission wave and receives
a reception wave is held by the holding unit 130 in the eardrum sound pressure acquisition
unit 142, and an arrangement of a device that estimates and acquires an eardrum sound
pressure based on vibration information is not particularly limited.
[0088] The cancellation point is one point on the eardrum. That is, the eardrum sound pressure
acquisition unit 142 acquires the eardrum sound pressure information. Since the eardrum
sound pressure information is used for the noise cancellation process, the high noise
canceling performance can be realized.
[0089] The reflection point is also desirably one point on the eardrum. In this case, the
eardrum vibration information is directly acquired, and thus, the eardrum sound pressure
acquisition unit 142 can acquire the eardrum sound pressure information based on the
eardrum vibration information. Accordingly, the eardrum sound pressure information
can be estimated with high accuracy.
[0090] On the other hand, the reflection point may be on the inner wall of the ear canal.
In this case, the eardrum sound pressure acquisition unit 142 estimates the eardrum
sound pressure information based on vibration information of two or more points on
the inner wall of the ear canal. For example, the eardrum sound pressure acquisition
unit 142 refers to a model having a correlation between a vibration of the inner wall
of the ear canal and a vibration of the eardrum to estimate the eardrum vibration
information based on the vibration information of two or more points on the inner
wall of the ear canal. Then, the eardrum sound pressure information is estimated based
on the estimation result of the vibration information of the eardrum. As a result,
even when the eardrum is not directly irradiated with a laser, it is possible to execute
the noise cancellation process using the eardrum sound pressure information. In addition,
the eardrum sound pressure acquisition unit 142 may measure the eardrum vibration
information and the vibration information of the inner wall of the ear canal and estimate
the sound pressure information of the eardrum position based on these measurement
results. In this case, the sound pressure information of the eardrum position can
be estimated with higher accuracy.
[0091] In addition, the eardrum sound pressure acquisition unit 142 can measure a self-generated
sound (for example, own voice) due to body conduction based on vibration information
of the inner wall of the ear canal. The eardrum sound pressure acquisition unit 142
can measure the self-generated sound based on left and right air propagation sound
wave information in addition to the vibration information of the inner wall of the
ear canal.
[0092] Note that whether the reflection point is the eardrum or the inner wall of the ear
canal can be determined based on, for example, information indicating a three-dimensional
shape to be described later.
[0093] Hereinafter, a state of distance measurement using the eardrum sound pressure acquisition
unit 142 realized as the laser distance measuring device will be described in detail
with reference to FIGS. 14 to 17.
[0094] FIG. 14 is a cross-sectional view illustrating a state of the inside of the ear canal
of the user's left ear. As illustrated in FIG. 14, an eardrum vibrating surface 14
forms a predetermined angle with respect to a lower wall 13 of the ear canal. In the
case of an adult, the eardrum vibrating surface 14 forms an angle of about 50 degrees
with respect to the lower wall 13 of the ear canal.
[0095] FIGS. 15 to 17 are views illustrating a state where the inside of the ear canal of
user's left ear illustrated in FIG. 14 is irradiated with a laser by the ear hole
opening device 100. FIG. 15 is a view from the same viewpoint as FIG. 14, FIG. 16
is a view of the viewpoint looking down from the Z-axis positive direction to the
Z-axis negative direction, and FIG. 17 is a view of the viewpoint from the vicinity
of the middle between the X-axis positive direction and the Z-axis positive direction
toward the origin. As illustrated in FIGS. 15 to 17, the eardrum 9 is irradiated with
a laser 16 by the eardrum sound pressure acquisition unit 142 (laser distance measuring
device). As illustrated in FIGS. 15 and 16, an irradiation direction 17 of the laser
16 and a vibration direction 15 of the eardrum 9 can intersect each other with a specific
angle. It is desirable to correct this angular difference in order to accurately estimate
the sound pressure information of the eardrum 9. The correction of the angular difference
may be performed by logical calculation or may be performed by physical control of
the laser irradiation direction to be described later.
[0096] As illustrated in FIGS. 15 and 16, it is desirable that the holding unit 130 hold
the eardrum sound pressure acquisition unit 142 at a position where the inner wall
of the ear canal 5 is not present on a straight line between the eardrum sound pressure
acquisition unit 142 and the eardrum 9. In other words, it is desirable that the eardrum
sound pressure acquisition unit 142 be held at a position where there is no obstacle
between the eardrum sound pressure acquisition unit 142 and the eardrum 9. As a result,
it is possible to directly reflect the laser emitted from the eardrum sound pressure
acquisition unit 142 to one point on the eardrum 9.
(2) Eardrum Sound Pressure Acquisition Process
[0097] Hereinafter, an eardrum sound pressure acquisition process will be described with
reference to FIGS. 18 to 20.
• First Example
[0098] FIG. 18 is a diagram for describing a model configuration example of an eardrum sound
pressure estimation process according to the present embodiment.
[0099] A laser diode 230 generates and emits a laser. The laser emitted from the laser diode
230 is separated into two directions by a beam splitter 231, and one beam thereof
passes through the beam splitter 232 and a focus lens 233 and reaches the eardrum
9. The laser reflected by the eardrum 9 passes through the focus lens 233, is reflected
by the beam splitter 232 and a mirror 234, passes through the beam splitter 237, and
is input to a photoelectric converter 238.
[0100] On the other hand, the other beam of the laser emitted from the laser diode 230 and
separated by the beam splitter 231 is input to an optical frequency converter 236.
A signal oscillated at a reference frequency by a reference frequency oscillator 235
is also input to the optical frequency converter 236. The optical frequency converter
236 modulates a frequency of the laser emitted from the laser diode 230 to the reference
frequency and outputs the reference frequency. The laser output from the optical frequency
converter 236 is reflected by the beam splitter 237 and input to the photoelectric
converter 238.
[0101] The laser that has passed through the beam splitter 237 is converted into a light
intensity signal by the photoelectric converter 238. The light intensity signal indicates
an eardrum vibration frequency that is frequency-modulated with the reference frequency.
The light intensity signal is converted into a signal of a frequency domain by a frequency
voltage converter 239, the converted signal is subjected to a band-limiting filter
240 and is input to a speed/acceleration converter 241. The signal after having been
subjected to band-limiting filter processing by the band-limiting filter 240 is an
eardrum vibration speed signal. The speed/acceleration converter 241 converts an eardrum
speed into an eardrum acceleration based on the eardrum speed signal, and outputs
a signal indicating the eardrum acceleration to the eardrum sound pressure estimation
unit 242. The eardrum sound pressure estimation unit 242 estimates an eardrum sound
pressure (sound pressure information of the eardrum 9) based on the eardrum acceleration.
Note that the eardrum sound pressure is estimated by the following formula.
Eardrum sound pressure PD = K·a
[0102] Here, a [m/s
2] is an acceleration signal obtained by the speed/acceleration converter 241. K [kg/m
2] is a constant composed of the area, the mass, and the tension of the eardrum, a
correction coefficient based on an entry angle of a laser into the eardrum, and the
like. Note that at least a part of the eardrum sound pressure acquisition process
may be performed by a digital circuit. For example, the processing of the speed/acceleration
converter 241 and the eardrum sound pressure estimation unit 242 may be performed
by the digital circuit. In addition, the eardrum sound pressure estimation unit 242
may include the function as the speed/acceleration converter 241.
• Second Example
[0103] A shape of an ear, particularly a shape of an ear canal and an arrangement of an
eardrum vary from person to person. Therefore, a laser irradiation point (that is,
a reflection point) is not necessarily located at the center of the eardrum in a state
where the ear hole opening device 100 is worn by a user.
[0104] Therefore, the eardrum sound pressure acquisition unit 142 may estimate sound pressure
information of the eardrum additionally based on information indicating a three-dimensional
shape of user's ear canal. For example, the eardrum sound pressure acquisition unit
142 controls a laser irradiation direction based on the information indicating the
three-dimensional shape of the ear canal and uses the eardrum as the reflection point.
As a result, the eardrum sound pressure can be estimated directly, and thus, the accuracy
can be improved.
[0105] The eardrum sound pressure acquisition unit 142 acquires the information indicating
the three-dimensional shape of the ear canal by scanning the ear canal while changing
a transmission direction of a transmission wave. Specifically, the eardrum sound pressure
acquisition unit 142 measures a distance while sequentially changing the laser irradiation
direction, thereby acquiring a map of the distance between the eardrum sound pressure
acquisition unit 142 and the reflection point as a scanning result. This distance
map is the information indicating the three-dimensional shape of the ear canal with
reference to the eardrum sound pressure acquisition unit 142.
[0106] FIG. 19 is a view illustrating a state of scanning of the ear canal using the ear
hole opening device 100 according to the present embodiment. As illustrated in FIG.
19, the laser 16 is emitted from the eardrum sound pressure acquisition unit 142 while
changing the irradiation direction. The ear hole opening device 100 acquires information
indicating a three-dimensional shape of a range 18 irradiated with the laser. Accordingly,
for example, the eardrum sound pressure acquisition unit 142 can search for a direction
in which the eardrum 9 can be directly irradiated with the laser.
[0107] A mechanism for acquiring the information indicating the three-dimensional shape
of the ear canal can be realized as, for example, a MEMS (micro electro mechanical
systems) scanner. Hereinafter, a process of estimating the eardrum sound pressure
using the MEMS scanner will be described with reference to FIG. 20.
[0108] FIG. 20 is a diagram for describing a model configuration example of the eardrum
sound pressure estimation process according to the present embodiment. The model configuration
example illustrated in FIG. 20 includes a MEMS scanner 243 between the beam splitter
232 and the focus lens 233 in the model configuration example illustrated in FIG.
18. The MEMS scanner 243 functions as an irradiation angle correction unit that corrects
and outputs an irradiation angle of an input laser. The MEMS scanner 243 can change
the irradiation direction of the laser input from the beam splitter 232. The eardrum
sound pressure acquisition unit 142 acquires the information indicating the three-dimensional
shape of the ear canal by controlling the MEMS scanner 243 so as to sequentially change
the laser irradiation direction. Then, the eardrum sound pressure acquisition unit
142 controls the MEMS scanner 243 such that a laser is emitted in a direction in which
the eardrum becomes the reflection point based on the information indicating the three-dimensional
shape of the ear canal.
(3) Utilization of Information Indicating Three-Dimensional Shape
•Personal Authentication
[0109] The authentication unit 155 may authenticate a user based on the information indicating
the three-dimensional shape of the ear canal acquired by the eardrum sound pressure
acquisition unit 142. For example, the authentication unit 155 compares a feature
amount of information indicating a three-dimensional shape of user's ear canal stored
in advance and a feature amount of the information indicating the three-dimensional
shape of the ear canal acquired by the eardrum sound pressure acquisition unit 142.
The authentication unit 155 determines whether the wearing user matches a user registered
in advance based on the comparison result. Since the shape of the ear canal varies
from person to person, the authentication is possible. Since even one person has different
left and right ear shapes regarding human ears, the authentication unit 155 can further
improve the authentication accuracy by performing the above comparison for the left
and right ears. The signal processing unit 151 may perform signal processing based
on the authentication result. For example, the signal processing unit 151 may perform
a noise cancellation process using a filter characteristic set in advance for each
user.
[0110] Hereinafter, a personal authentication process using information indicating the three-dimensional
shape of the ear canal will be described with reference to FIG. 21.
[0111] FIG. 21 is a sequence diagram illustrating an example of flow of the personal authentication
process executed by the ear hole opening device 100 and a terminal device according
to the present embodiment. As illustrated in FIG. 21, the ear hole opening device
100 and a terminal device 800 are involved in this sequence. The terminal device 800
is an arbitrary device such as a smartphone, a tablet terminal, and an agent device.
[0112] As illustrated in FIG. 21, the ear hole opening device 100 has not yet been worn
by a user and is in a wearing standby state (Step S102). In addition, the terminal
device 800 is not connected to the ear hole opening device 100 and is in a connection
standby state (Step S104).
[0113] As illustrated in FIG. 21, the ear hole opening device 100 first determines whether
a measured distance is within a predetermined value (Step S106). The predetermined
value herein is, for example, the maximum value of an ear canal length. If the measured
distance is within the predetermined value, it is understood that the distance measurement
is performed at least in the ear canal. When it is determined that the measured distance
is not within the predetermined value (Step S106/NO), the process returns to Step
S106 again, and the wearing standby state is continued.
[0114] On the other hand, when it is determined that the measured distance is within the
predetermined value (Step S106/YES), the ear hole opening device 100 acquires the
information indicating the three-dimensional shape in the ear canal and extracts the
feature amount (Step S108).
[0115] Next, the ear hole opening device 100 compares the extracted feature amount with
the feature amount stored in advance, and determines whether both the feature amounts
match (S110). When it is determined that both the feature amounts do not match (Step
S110/NO), the process returns to Step S106 again.
[0116] When it is determined that both the feature amounts match (Step S110/YES), the ear
hole opening device 100 transmits authentication information indicating that the user
authentication has been completed to the terminal device 800 (Step S112). The terminal
device 800 receives and confirms the authentication information from the ear hole
opening device 100 (Step S114), performs a connection process, and transmits connection
completion notification to the ear hole opening device 100 (Step S116). As a result,
the terminal device 800 is turned into a connection completion state. The ear hole
opening device 100 receives the connection completion notification from the terminal
device 800 (Step S118). As a result, the ear hole opening device 100 is turned into
the connection completion state.
• Wearing Detection
[0117] The operation control unit 153 determines whether the ear hole opening device 100
is worn based on the information indicating the three-dimensional shape acquired by
the eardrum sound pressure acquisition unit 142. For example, the operation control
unit 153 determines that the ear hole opening device 100 is worn when the measured
distance obtained by the eardrum sound pressure acquisition unit 142 is within the
predetermined value, and determines that the ear hole opening device 100 is not worn
when the measured distance exceeds the predetermined value. The predetermined value
herein is, for example, the maximum value of an ear canal length. Then, the operation
control unit 153 controls an operation of the ear hole opening device 100 based on
the determination result. For example, the operation control unit 153 may cause the
signal processing unit 151 to start generating a noise cancellation signal when determining
that the ear hole opening device 100 is worn. In addition, the operation control unit
153 may cause the driver 110 to start outputting an output signal when determining
that the ear hole opening device 100 is worn. As a result, the operation of the ear
hole opening device 100 is automatically started when the user wears the ear hole
opening device 100, and thus, an operation burden on the user is reduced. In addition,
when determining that the ear hole opening device 100 is not worn, the operation control
unit 153 may stop the generation of the noise cancellation signal and the output of
the output signal. As a result, the operation of the ear hole opening device 100 is
stopped or partly stopped in the non-wearing state, and thus, wasteful power consumption
can be prevented.
• Correction of Reproduced Sound
[0118] The signal processing unit 151 may adjust the sound quality of the output signal
output from the driver 110 based on the information indicating the three-dimensional
shape of the ear canal. For example, the signal processing unit 151 performs a process
of attenuating a sound having an excessively reverberating frequency and emphasizing
a sound having an excessively reduced frequency based on the information indicating
the three-dimensional shape of the ear canal. As a result, it becomes possible to
provide a user with the optimum sound quality in response to the three-dimensional
shape of the user's ear canal.
(4) Other
• Howling Canceller
[0119] The ear hole opening device 100 may detect howling that occurs when the microphone
141 collects the audio output by the driver 110. Then, when detecting the howling,
the ear hole opening device 100 may stop or temporarily stop the output from the driver
110 or the noise cancellation process and notify the wearing of the stop. In addition,
the situation where the howling has occurred may be transmitted to the outside via
a wireless communication unit 170 to be described later.
• Calibration Signal
[0120] The ear hole opening device 100 outputs a predetermined calibration signal from the
driver 110, and collects the calibration signal by the microphone 141 so that transfer
characteristics from the driver 110 to the microphone 141 can be obtained. This transfer
characteristics depend on an ear shape and a worn state of each wearer. Therefore,
the ear hole opening device 100 can perform the more suitable output configuration
of the driver 110 by actually measuring the transfer characteristics from the driver
110 to the microphone 141 in the state of being worn by the user. In addition, the
ear hole opening device 100 can adaptively configure the output configuration using
the output signal and the actual audio signal collected from the microphone 141.
<1.7. Summary>
[0121] The first embodiment has been described in detail above. As described above, the
ear hole opening device 100 according to the first embodiment opens the ear hole to
the outside through the opening portion 131 while holding the audio information acquisition
unit 140 acquiring the audio information in the space closer to the eardrum than the
tragus using the holding unit 130 that abuts on the cavum concha or the inner wall
of the ear canal. Then, the ear hole opening device 100 generates the noise cancellation
signal based on the audio information acquired by the audio information acquisition
unit 140. For example, the ear hole opening device 100 performs the noise cancellation
process using the position of the audio information acquisition unit 140 or the eardrum
position as the cancellation point. Since the position near the eardrum or the eardrum
is the cancellation point, the high noise canceling performance can be realized.
[0122] As the ear hole opening device 100 is equipped with the noise cancellation function
by such active processing, various effects are exhibited. Hereinafter, the effects
exhibited in the present embodiment will be described with a specific example.
[0123] For example, an office or the like is filled with noise of a lower frequency than
a speech voice such as air-conditioning sound in the office and incoming running sounds
of trains or cars leaking from the outside of the office. The ear hole opening device
100 cancels this noise. In this case, the user wearing the ear hole opening day bus
100 can communicate more smoothly with others, and a mental load and a physical load
are reduced.
[0124] In addition, a middle frequency band such as the speech voice is not subject to noise
canceling, the speech voice is not canceled, and further the speech voice reaches
the eardrum as it is since the ear hole is opened. For this reason, the user wearing
the ear hole opening device 100 does not need to remove the ear hole opening device
100 each time to have a conversation.
[0125] In addition, the air inside and outside the ear canal can freely move since the ear
hole is open. For this reason, the ear hole opening device 100 hardly gives the user
discomfort caused by the humidity and temperature in the ear canal. Accordingly, the
user can wear the ear hole opening device 100 for a long time.
[0126] In addition, the ear hole opening device 100 can increase a signal-to-noise ratio
by reducing ambient noise when outputting music or a voice. This means that the user
can easily listen to a target sound even if the music or voice has the same volume.
In other words, the volume of the music or voice that needs to be output in order
to maintain the same signal-to-noise ratio is suppressed. Therefore, it is possible
to reduce a sound of the music or voice output by the ear hole opening device 100
leaking to the surroundings.
[0127] Further, the user's own voice (own voice), a beating sound, a masticating sound,
a sound generated at the time of swallowing, a blood-flowing sound, a breathing sound,
a vibration sound transmitted through a body during walking, a rustling sound of a
cable or the like, and a rubbing sound of a portion where an earpiece comes into contact
with the ear canal, and the like are not emphasized since the ear hole is open.
<<2. Second Embodiment>>
[0128] A second embodiment relates to a noise cancellation process using an audio processing
device (headphones) having a microphone arranged near an entrance of an ear canal.
<2.1. Technical Problem>
[0129] First, a noise cancellation process using headphones according to a comparative example
will be described, and a technical problem of the present embodiment will be described
with reference to FIGS. 22 to 27.
[0130] FIG. 22 is a diagram illustrating a configuration example of headphones 380-1 equipped
with an FB-NC function. As illustrated in FIG. 22, the headphones 380-1 equipped with
the FB-NC function includes a housing 381 and an ear pad 382. The housing 381 and
the ear pad 382 cover (typically seal) one ear of a user wearing the headphones 380-1
equipped with the FB-NC function. The housing 381 stores various devices configured
for signal processing, such as a driver (speaker) 383, an FB-NC microphone 384, and
an FB filter 385 (characteristic: -β).
[0131] The FB-NC microphone 384 collects ambient sounds and generates an audio signal. The
FB filter 385 generates a noise cancellation signal by a noise cancellation process
of the FB scheme based on the audio signal generated by the FB-NC microphone 384.
The driver 383 outputs audio based on the noise cancellation signal generated by the
FB filter 385. As a result, it is possible to cancel noise after passive sound insulation
using passive sound insulation elements such as the housing 381, the ear pad 382,
and user's head. This noise cancellation process will be described in detail with
reference to FIG. 23.
[0132] FIG. 23 is a diagram illustrating a model configuration example of the noise cancellation
process using the headphones 380-1 equipped with the FB-NC function illustrated in
FIG. 22. Symbols of blocks illustrated in the model configuration example as illustrated
in FIG. 23 indicate characteristics (that is, transfer functions) corresponding to
specific circuit parts, circuit systems in a noise cancellation system, or the like.
The respective symbols have meanings as follows.
H: Spatial characteristic of space 392 from driver 383 to FB-NC microphone 384
M: Characteristic of FB-NC microphone 384
A: Characteristic of amplifier 391
D: Characteristic of driver 383
F: Characteristic of passive sound insulation element 393
-β: Characteristic of FB filter 385
[0133] In addition, N represents noise, and P represents a sound pressure at an eardrum
position.
[0134] As illustrated in FIG. 23, the audio signal generated by the FB-NC microphone 384
is input to the FB filter 385. The FB filter 385 generates the noise cancellation
signal based on the input audio signal. The noise cancellation signal generated by
the FB filter 385 is amplified by the amplifier 391 and output from the driver 383.
The audio output from the driver 383 passes through the space 392, and then, interferes
with the noise N that has passed through the passive sound insulation element 393
in the space 394 to cancel the noise N. The noise N that has not been canceled is
collected by the FB-NC microphone 384 and transmitted to the eardrum as the eardrum
position sound pressure P.
[0135] A cancellation point is a position of the FB-NC microphone 384. When a sensitivity
function is calculated for a residual signal r (residual noise) at the position of
the FB-NC microphone 384, the following formula is obtained.
[0136] As illustrated in Formula (B1), the sensitivity function is minimized by increasing
an NC filter β.
[0137] Here, the FB filter 385 includes an ADC and a DAC. The performance of FB-NC is improved
by suppressing the influence caused by a system delay such as a digital processing
delay due to the ADC and DAC. Meanwhile, as a parameter contributing to the delay,
there is a distance delay in an audio space in addition to the system delay. This
distance delay also affects the performance of FB-NC.
[0138] FIG. 24 is a graph illustrating an example of a phase characteristic corresponding
to a distance from the headphone driver to the FB-NC microphone. FIG. 24 illustrates
the phase characteristics when the distance from the headphone driver to the FB-NC
is 20 mm, 50 mm, or 100 mm. As illustrated in FIG. 24, a phase rotation increases
as the distance from the headphone driver to the FB-NC increases. Then, the limit
performance of FB-NC deteriorates as the phase rotation increases. From the above,
it can be said that it is desirable to reduce the distance between the driver and
the FB-NC in order to prevent the performance deterioration of FB-NC caused by the
distance delay.
[0139] In the headphones 380-1 equipped with the FB-NC function illustrated in FIG. 22,
the FB-NC microphone 384 is arranged at a position close to the driver 383 inside
the housing 381. Accordingly, the above-described distance delay is small. However,
the position of the FB-NC microphone 384 is far from a position of the eardrum 9 which
is a point where a sound pressure (sound pressure caused by noise) is desirably minimized.
For this reason, the minimization of the sound pressure at the position of the FB-NC
microphone 384 does not necessarily lead to the minimization of the sound pressure
at the position of the eardrum 9. That is, there is a risk that the performance of
FB-NC may deteriorate.
[0140] Ideally, it is considered that the above-described distance delay can be eliminated
by arranging the FB-NC microphone at the position of the eardrum 9. Such headphones
equipped with the FB-NC function will be described with reference to FIG. 25.
[0141] FIG. 25 is a diagram illustrating an example of headphones 380-2 equipped with the
FB-NC function. As illustrated in FIG. 25, the headphones 380-2 equipped with the
FB-NC function have the FB-NC microphone 384 arranged near the eardrum 9. For this
reason, the minimization of the sound pressure at the position of the FB-NC microphone
384 easily leads to the minimization of the sound pressure at the position of the
eardrum 9, and the deterioration of the performance of FB-NC can be suppressed. However,
there is a risk that the performance of FB-NC may deteriorate due to the influence
of the above-described distance delay since the distance between the driver 383 and
the FB-NC microphone 384 is large.
[0142] In summary, the phase delay derived from the distance is small, but the sound pressure
at the eardrum position is not always minimized according to the arrangement of the
FB-NC microphone 384 illustrated in FIG. 22. On the other hand, the sound pressure
at the eardrum position is fed back, but the phase delay derived from the distance
is large according to the arrangement of the FB-NC microphone 384 illustrated in FIG.
25.
[0143] The following two guidelines can be considered in order to improve the performance
of FB-NC in the headphones as described above, but these guidelines contradict each
other on the assumption that the position of the driver is fixed.
First guideline: Reduce the distance delay: Arrange the FB-NC microphone close to
the driver
Second guideline: Set the cancellation point close to the eardrum: Arrange the FB-NC
microphone far from the driver
[0144] Therefore, a mechanism for a noise cancellation process that eliminates the contradiction
is proposed in the present embodiment. Specifically, the mechanism for the noise cancellation
process that uses an error microphone installed near the eardrum position in addition
to the FB-NC microphone installed near the driver is proposed in the present embodiment.
According to this mechanism, it is possible to minimize the sound pressure at the
cancellation point close to the eardrum position using the error microphone while
suppressing the distance delay using the FB-NC microphone.
[0145] Headphones equipped with the NC function include not only the above-described FB
type but also the FF type and a combination type of FB and FF. In general, it is said
that the headphones with the NC function of the combination type has the highest NC
performance among these types. For reference, the headphones equipped with the NC
function of the combination type will be described with reference to FIGS. 26 and
27.
[0146] FIG. 26 is a diagram illustrating a configuration example of headphones 380-3 equipped
with the combination type NC function. As illustrated in FIG. 26, the headphones 380-3
equipped with the combination type NC function includes an FF-NC microphone 386 and
an FF filter 387 having a characteristic -α, for the FF-NC, in addition to the configuration
of the headphones 380-1 illustrated in FIG. 22.
[0147] FIG. 27 is a diagram illustrating a model configuration example of a noise cancellation
process using the headphones 380-3 equipped with the combination type NC function
illustrated in FIG. 26. In the model configuration example illustrated in FIG. 27,
constituent elements for the FF-NC are added to the model configuration example illustrated
in FIG. 23. Hereinafter, such added blocks will be described. Symbols in the added
blocks have meanings as follows.
M1: Characteristic of FB-NC microphone 384
M2: Characteristic of FF-NC microphone 386
-α: Characteristic of FF filter 387
[0148] As illustrated in FIG. 27, an audio signal generated based on noise N collected by
the FF-NC microphone 386 is input to the FF filter 387. The FF filter 387 generates
a noise cancellation signal by the noise cancellation process of the FF scheme based
on the input audio signal. An adder 395 synthesizes the noise cancellation signal
generated by the FF filter 387 and the noise cancellation signal generated by the
FB filter 385 to generate a synthesized signal. The synthesized signal is output from
the driver 383 via the amplifier 391. The audio output from the driver 383 passes
through the space 392, and then, interferes with the noise N that has passed through
the passive sound insulation element 393 in the space 394 to cancel the noise N. The
noise N that has not been canceled is collected by the FB-NC microphone 384 and transmitted
to the eardrum as the eardrum position sound pressure P.
<2.2. Exterior Configuration of Headphones>
[0149] Hereinafter, an example of an exterior configuration of the audio processing device
(headphones) according to the present embodiment will be described with reference
to FIGS. 28 to 30.
[0150] FIGS. 28 and 29 are diagrams for describing an example of the exterior configuration
of headphones 300 according to the present embodiment. FIG. 28 illustrates the exterior
configuration in a state where the headphones 300 are worn by a user. FIG. 29 illustrates
the exterior configuration of the headphones 300 illustrated in FIG. 28 as viewed
from an inner space 30 illustrated in FIG. 28. Hereinafter, the exterior configuration
of the headphones 300 will be described mainly with reference to FIG. 28.
[0151] As illustrated in FIG. 28, the headphones 300 include a housing 301 and an ear pad
302. One ear of the user wearing the headphones 300 is covered (typically sealed)
by the housing 301 and the ear pad 302. The housing 301 stores various devices configured
for signal processing such as an audio output unit 310, audio input units 320-1 and
320-2, and a filter circuit. The ear pad 302 comes into contact with user's head at
a contact surface 302a. The ear pad 302 is formed using an elastic body such as sponge,
and is in close contact with the user's head while being deformed in accordance with
the user's head, and forms the inner space 30. The inner space 30 is a space formed
by the housing 301, the ear pad 302, and the user's head. The inner space 30 may be
a sealed space isolated from an outer space 31 that is a space on the outside or may
be connected to the outer space 31. Noise after passive sound insulation by passive
sound insulation elements, such as the housing 301, the ear pad 302, and the user's
head, arrives at the inner space 30. A wall portion 301a of the housing 301 is in
contact with the inner space 30, and an outer wall portion 301b of the housing 301
is in contact with the outer space 31.
[0152] The audio output unit 310 outputs audio to a space based on the audio signal. The
audio output unit 310 can also be referred to as a driver. The driver 310 is provided
in the housing 301. Then, the driver 310 outputs audio toward the inner space 30 that
is a space closer to the eardrum than the housing 301. For example, the driver 310
outputs the audio to the space based on the noise cancellation signal generated based
on sound collection results obtained by the audio input units 320-1 to 320-3. As a
result, the noise that has arrived at the inner space 30 can be canceled.
[0153] The audio input units 320 (320-1 to 320-3) collect ambient sounds and generate audio
signals. As illustrated in FIG. 28, the three audio input units 320 are arranged on
one ear side of the user in the state of being worn by the user.
[0154] The audio input unit 320-1 is a microphone that performs sound collection for FB-NC
(that is, the FB-NC microphone). The FB-NC microphone 320-1 is arranged at a position
where a distance from the eardrum 9 of the user is shorter than the audio input unit
320-2 and longer than the audio input unit 320-3 in a state where the headphones 300
are worn by the user. More specifically, the FB-NC microphone 320-1 is arranged at
a position where noise is collected through shielding objects, that is, after being
subjected to passive sound insulation in the state where the headphones 300 are worn
by the user. Further, it is desirable that the FB-NC microphone 320-1 be arranged
between the eardrum 9 of the user and the driver 310. The shielding objects herein
are passive sound insulation elements and correspond to the housing 301, the ear pad
302, and the user's head. As illustrated in FIG. 28, the FB-NC microphone 320-1 is
provided on the wall portion 301a of the housing 301 on the inner space 30 side. Then,
the FB-NC microphone 320-1 collects audio of the inner space 30 and generates an audio
signal. The audio collected at this time contains noise after passive sound insulation
by the passive sound insulation elements. The FB-NC microphone 320-1 corresponds to
a first audio input unit, and the audio signal generated by the FB-NC microphone 320-1
can also be referred to as a first audio signal. The audio signal generated by the
FB-NC microphone 320-1 is input to the FB filter and used to generate the noise cancellation
signal.
[0155] The audio input unit 320-2 is a microphone that performs sound collection for FF-NC
(that is, the FF-NC microphone). In addition, the FF-NC microphone 320-2 is arranged
at a position where the distance from the eardrum 9 of the user is the longest in
the state where the headphones 300 are worn by the user. More specifically, the FF-NC
microphone 320-2 is arranged at a position where noise is collected without passing
through shielding objects, that is, without being subjected to passive sound insulation
in the state where the headphones 300 are worn by the user. As illustrated in FIG.
28, the FF-NC microphone 320-2 is provided on the wall portion 301b of the housing
301 on the outer space 31 side. Then, the FF-NC microphone 320-2 collects audio of
the outer space 31 and generates an audio signal. The audio collected at this time
contains noise that has arrived at the outer space 31. The FF microphone 320-2 corresponds
to a second audio input unit, and the audio signal generated by the FF microphone
320-2 can also be referred to as a second audio signal. Here, the FF-NC microphone
320-2 may be exposed to the outer space 31 or is not necessarily exposed. For example,
the FF-NC microphone 320-2 may be embedded in the housing 301 and may collect a wrap-around
sound or a sound transmitted through a cover such as a cloth. The audio signal generated
by the FF-NC microphone 320-2 is input to the FF filter and used to generate the noise
cancellation signal.
[0156] The audio input unit 320-3 is an audio input unit that is arranged to be spaced apart
from the housing 301, and is a microphone (hereinafter also referred to as an ear
canal microphone) that is arranged near the entrance of the ear canal 5 in the state
where the headphones 300 are worn by the user. The ear canal microphone 320-3 is arranged
at a position where the distance from the eardrum 9 of the user is the shortest in
the state where the headphones 300 are worn by the user. The ear canal microphone
320-3 is arranged at a position where noise is collected through the shielding objects
in the state where the headphones 300 are worn by the user. As illustrated in FIG.
28, the ear canal microphone 320-3 is arranged in the inner space 30. Here, the ear
canal microphone 320-3 is held near the entrance of the ear canal 5 of the user by
a holding unit 303. Then, the ear canal microphone 320-3 collects noise after passive
sound insulation by the passive sound insulation elements, and generates an audio
signal. The ear canal microphone 320-3 corresponds to a third audio input unit, and
the audio signal generated by the ear canal microphone 320-3 can also be referred
to as a third audio signal. The audio signal generated by the ear canal microphone
320-3 is used to generate the noise cancellation signal.
[0157] The holding unit 303 engages with the vicinity of the entrance of the ear canal 5
(for example, the intertragic notch), and holds the ear canal microphone 320-3 at
the vicinity of the entrance of the ear canal 5. An outer diameter of the ear canal
microphone 320-3 is formed so as to be much smaller than an inner diameter of the
ear hole. Therefore, the ear hole of the listener is not blocked even in the state
where the ear canal microphone 320-3 is held at the vicinity of the entrance of the
ear canal 5 by the holding unit 303.
[0158] In addition, the holding unit 303 includes opening portions 304 that open the entrance
(ear hole) of the ear canal 5 to the outside even in the state of holding the ear
canal microphone 320-3. The outside is a space where noise is passively sound-insulated,
and is the inner space 30. In the example illustrated in FIG. 28, the holding unit
303 is a ring-shaped structure, the ear canal microphone 320-3 is provided in a part
where rod-shaped first support members 305 provided in a ring inner direction are
combined near the ring center, and all the other parts of the ring-shaped structure
are opening portions 304. The rod-shaped first support member 305 is gently curved,
and the plurality of first support members 305 and the holding unit 303 form a hemispherical
shape having the holding unit 303 as a split plane. The holding unit 303 abuts on
an inner wall of the cavum concha 4 or the ear canal 5 of user's one ear in the state
where the headphones 300 are worn by the user. Then, the holding unit 303 holds the
ear canal microphone 320-3 in the space closer to the eardrum 9 than the tragus 6.
Such a configuration of the holding unit 303 is the same as the configuration of the
holding unit 130 according to the first embodiment. Note that the holding unit 303
is not limited to the ring-shaped structure, and may have an arbitrary shape that
can provide the ear canal microphone 320-3 as long as a hollow structure is provided.
Examples of the shape of the holding unit 303 are illustrated in FIG. 30. FIG. 30
is a view illustrating examples of the shape of the holding unit 303 of the headphones
300 according to the present embodiment. As illustrated in FIG. 30, a holding unit
303A has a ring-shaped structure, a holding unit 303B has a ring-shaped structure
from which a part has been cut and removed, and a holding unit 303C has a ring-shaped
structure divided into three parts. In this manner, the shape of the holding unit
303 may be a ring-shaped structure or a similar type thereof.
[0159] A second support member 306 is a structure in which one end is connected to the housing
301 and the other end is connected to the holding unit 303. As illustrated in FIG.
28, the second support member 306 may be a rod-shaped structure curved in an S shape.
In addition, a plurality of the second support members 306 may be provided.
[0160] Note that FIGS. 28 and 29 illustrate an exterior configuration on the right ear side
of the headphones 300, an exterior configuration on the left ear side is bilaterally
symmetric with the exterior configuration on the right ear side. The headphones 300
may be configured to be separated and independent from each other between the right
ear side and the left ear side, or may be integrally configured. In addition, the
headphones 300 can have an arbitrary structure such as a sealed type, an open type,
an overhead type, a neckband type, and an ear hook type.
<2.3. Internal Configuration of Headphones>
[0161] FIG. 31 is a diagram illustrating an example of an internal configuration of the
headphones 300 according to the present embodiment. As illustrated in FIG. 31, the
headphones 300 include the audio output unit 310, the audio input unit 320, a control
unit 330, and a sensor unit 370.
• Audio Output Unit 310
[0162] The audio output unit 310 (driver) has a function of outputting audio based on an
audio signal. The driver 310 outputs audio to a space based on an output signal output
from a signal processing unit 331.
• Audio Input Unit 320
[0163] The audio input unit 320 includes a microphone (hereinafter also simply referred
to as a microphone) that detects ambient sounds and generates an audio signal indicating
the detection result by the microphone.
• Control Unit 330
[0164] The control unit 330 functions as an arithmetic processing device and a control device,
and controls the entire processing performed by the headphones 300 according to various
programs. The control unit 330 is realized by an electronic circuit, for example,
a central processing unit (CPU), a micro-processing unit (MPU), a demand-side platform
(DSP), or the like. Note that the control unit 330 may include a read-only memory
(ROM) that stores programs to be used, calculation parameters, and the like, and a
random-access memory (RAM) that temporarily stores parameters that change as appropriate.
Typically, the control unit 330 is stored in the housing 301.
[0165] As illustrated in FIG. 31, the control unit 330 includes a signal processing unit
331 and an operation control unit 333.
[0166] The signal processing unit 331 has a function of generating a noise cancellation
signal for noise based on the audio signal generated by the audio input unit 320.
The signal processing unit 331 generates a plurality of noise cancellation signals
based on the three audio signals generated by the three audio input units 320-1 to
320-3. For example, the signal processing unit 331 performs at least one of the noise
cancellation process of the FB scheme and the noise cancellation process of the FF
scheme to generate the plurality of noise cancellation signals. The signal processing
unit 331 generates an audio signal (hereinafter also referred to as an output signal)
based on the plurality of generated noise cancellation signals, and outputs the audio
signal to the driver 110. For example, the output signal may be a signal obtained
by synthesizing the plurality of noise cancellation signals, or may be a synthesized
signal obtained by synthesizing another audio signal such as a music signal acquired
from a sound source and the noise cancellation signal. The signal processing unit
331 includes various constituent elements for noise cancellation processes which will
be described with reference to FIGS. 32 to 37 and the like. For example, the signal
processing unit 331 includes: various filter circuits configured to generate a noise
cancellation signal; an adaptive control unit configured to adaptively control the
filter circuits; an adder configured to synthesize signals; an internal model; a device
configured to generate and analyze a measurement signal to be described later; and
the like. In addition, the signal processing unit 331 also includes circuits such
as an amplifier, an ADC, and a DAC.
• Operation Control Unit 333
[0167] The operation control unit 333 has a function of controlling an operation mode of
the headphones 300. The operation control unit 333 stops or activates some or all
of functions of the headphones 300. For example, the operation control unit 333 controls
the stop/activation of the function of the headphones 300 based on a detection result
obtained by the sensor unit 370.
• Sensor Unit 370
[0168] The sensor unit 370 is a device that detects information on the headphones 300 or
information on a user wearing the headphones 300. The sensor unit 370 can include
various sensor devices such as a pressure-sensitive sensor, a gyro sensor, an acceleration
sensor, and a body temperature sensor. For example, the sensor unit 370 detects deformation
of a member constituting the headphones 300, such as the ear pad 302, by the pressure-sensitive
sensor. As a result, it is possible to determine wearing/non-wearing of the headphones
300.
<2.4. Details of Noise Cancellation Process>
(1) First Noise Cancellation Process
[0169] A first noise cancellation process includes processing using the ear canal microphone
320-3 as an error microphone of the FB-NC. Specifically, the signal processing unit
331 generates a third noise cancellation signal by FB-NC using the ear canal microphone
320-3 as a cancellation point based on the third audio signal generated by the ear
canal microphone 320-3. Since the ear canal microphone 320-3 is arranged near the
eardrum 9, the cancellation point of FB-NC can be set to be close to the eardrum 9.
That is, the above second guideline is satisfied.
[0170] Further, the first noise cancellation process includes processing using the FB-NC
microphone 320-1 as an error microphone of FB-NC. Specifically, the signal processing
unit 331 generates a first noise cancellation signal by FB-NC using the FB-NC microphone
320-1 as a cancellation point based on the first audio signal generated by the FB-NC
microphone 320-1. Since the FB-NC microphone 320-1 is arranged to be close to the
driver 310, the above-described phase rotation due to the distance decreases. That
is, the above first guideline is satisfied.
[0171] In this manner, it is possible to satisfy both the first guideline and the second
guideline according to the first noise cancellation process. Therefore, it is possible
to minimize the sound pressure at the cancellation point, which is close to the eardrum
position, while suppressing the distance delay according to the first noise cancellation
process. Hereinafter, details of the first noise cancellation process will be described
with reference to FIG. 32.
[0172] FIG. 32 is a diagram illustrating a model configuration example of the first noise
cancellation process using the headphones 300 according to the present embodiment.
Symbols in the blocks illustrated in FIGS. 32 to 37 have meanings as follows.
H1: Characteristic of space 401 from driver 310 to FB-NC microphone 320-1
H2: Characteristic of space 402 from FB-NC microphone 320-1 to ear canal microphone
320-3 (more precisely, difference characteristic between space from driver 310 to
FB-NC microphone 320-1 and space from driver 310 to ear canal microphone 320-3)
F1: Characteristic of space 403 from noise source to FB-NC microphone 320-1
F2: Characteristic of space 404 from noise source to ear canal microphone 320-3
M1: Characteristic of FB-NC microphone 320-1
M2: Characteristic of FF-NC microphone 320-2
M3: Characteristic of ear canal microphone 320-3
A: Characteristic of amplifier 421
D: Characteristic of driver 310
-α: Characteristic of FF filter 414
-β1: Characteristic of first FB filter 411
-β2 Characteristic of second FB filter 412
-β3: Characteristic of third FB filter 413
H1': Simulated characteristic of space 401
H2': Simulated characteristic of space 402
M1': Simulated characteristic of FB-NC microphone 320-1
M3': Simulated characteristic of ear canal microphone 320-3
[0173] In addition, N represents noise, and P represents a sound pressure at an eardrum
position.
[0174] First, a noise cancellation process relating to the first FB filter 411 will be described.
An audio signal generated based on audio collected by the FB-NC microphone 320-1 is
input to the first FB filter 411. The first FB filter 411 performs the noise cancellation
process of the FB scheme using the FB-NC microphone 320-1 as a cancellation point
based on the input audio signal and generates a noise cancellation signal (first noise
cancellation signal). The noise cancellation signal generated by the first FB filter
411 is synthesized with noise cancellation signals generated by the second FB filter
412 and the FF filter 414 by an adder 431. The synthesized signal is amplified by
the amplifier 421 and output from the driver 310.
[0175] Next, a noise cancellation process relating to the FF filter 414 will be described.
An audio signal generated based on audio collected by the FF-NC microphone 320-2 is
input to the FF filter 414. The FF filter 414 generates the noise cancellation signal
(second noise cancellation signal) by the noise cancellation process of the FF scheme
based on the input audio signal. The noise cancellation signal generated by the FF
filter 414 is synthesized with the noise cancellation signals generated by the first
FB filter 411 and the second FB filter 412 by the adder 431. The synthesized signal
is amplified by the amplifier 421 and output from the driver 310.
[0176] Finally, a noise cancellation process relating to the second FB filter 412 will be
described. The ear canal microphone 320-3 collects audio and generates an audio signal.
An adder 432 subtracts a signal, obtained by applying internal models (characteristics:
D', H
1', H
2', and M
3') illustrated in blocks 441, 442, 443, and 444 to the output signal input to the
driver 310, from the audio signal generated by the ear canal microphone 320-3 to perform
the synthesis. The internal models herein have characteristics that simulate characteristics
from the input of the output signal to the driver 310 to the generation of the third
audio signal. The synthesized signal is input to the second FB filter 412. The second
FB filter 412 performs the noise cancellation process of the FB scheme using the ear
canal microphone 320-3 as a cancellation point based on the input audio signal, and
generates the noise cancellation signal (third noise cancellation signal). The noise
cancellation signal generated by the second FB filter 412 is synthesized with noise
cancellation signals generated by the first FB filter 411 and the FF filter 414 by
an adder 431. The synthesized signal is amplified by the amplifier 421 and output
from the driver 310.
[0177] The audio output from the driver 310 first passes through the space 401 and then
interferes with noise N that has passed through the space 403 in a space 405 to cancel
the noise N. The noise N that has not been canceled is collected by the FB-NC microphone
320-1. In addition, the audio output from the driver 310 further passes through the
space 402 and then interferes with noise N that has passed through the space 404 in
a space 406 to cancel the noise N. The noise N that has not been canceled is collected
by the ear canal microphone 320-3 and transmitted to the eardrum as the eardrum position
sound pressure P.
[0178] The details of the first noise cancellation process have been described above. According
to the first noise cancellation process, the internal model is introduced. Hereinafter,
a description will be given in detail regarding a fact that noise canceling performance
can be improved by introducing the internal model.
[0179] First, the output signal input to the driver 310 is defined as y. Then, the sound
pressure P at the position of the ear canal microphone 320-3 is expressed by the following
formula.
[0181] As described above, the output signal y is expressed as the following formula.
[0182] With Formulas (B2) and (B6), a sensitivity function P at the position of the ear
canal microphone 320-3 is expressed by the following formula.
[0183] The term illustrated in the following Formula (B8) in the sensitivity function P
illustrated in Formula (B7) can be omitted if the respective simulated characteristics
included in the internal models match, that is, if M
3 = M
3', D = D', H
1 = H
1', and H2 = H2'.
[0184] On the other hand, the term illustrated in the following Formula (B9) in the sensitivity
function P illustrated in Formula (B7) can be omitted by designing β
2, which is a designable parameter, according to the following Formula (B10).
[0185] When β
2 designed according to Formula (B10) is put into Formula (B9), the following formula
is obtained.
[0186] As described above, when the omitted term is excluded from Formula (B7), the sensitivity
function P is expressed by the following formula.
[0187] From the above Formula (B12), it is understood that the sensitivity function P can
be minimized by maximizing β
1. That is, it is understood that the sensitivity function at the position of the ear
canal microphone 320-3 closer to the eardrum can be minimized by maximizing a gain
of a system having the FB-NC microphone 320-1 with a little delay. As described above,
it can be said that noise can be canceled at the position of the ear canal microphone
320-3 closer to the eardrum by introducing the internal model.
(2) Second Noise Cancellation Process
[0188] A second noise cancellation process is a process using the ear canal microphone 320-3
for FF-NC. As the second noise cancellation process, the ear canal microphone 320-3
may be used as an error microphone for adaptive FF-NC, and may be used to set a fixed
FF-NC filter. Hereinafter, these will be described in order.
-Case of Using Ear Canal Microphone 320-3 as Error Microphone
[0189] The ear canal microphone 320-3 may be used as an error microphone for adaptive processing
in FF-NC. The adaptive processing is a method of adaptively changing a filter characteristic
so as to minimize an error signal at an error microphone position. Specifically, the
signal processing unit 331 generates the second noise cancellation signal by the FF-NC
based on the second audio signal generated by the FF-NC microphone 320-2. The signal
processing unit 331 adaptively controls the filter characteristic of the FF filter
used for this FF-NC based on the third audio signal generated by the ear canal microphone
320-3. According to this method, the error microphone position of FF-NC is close to
the eardrum 9, and thus, a high noise canceling effect is expected. Details of the
second noise cancellation process when the ear canal microphone 320-3 is used as the
error microphone will be described with reference to FIG. 33.
[0190] FIG. 33 is a diagram illustrating a model configuration example of the second noise
cancellation process using the headphones 300 according to the present embodiment.
Since the noise cancellation process relating to the first FB filter 411 is the same
as described above with reference to FIG. 32, the description thereof is omitted here.
[0191] Hereinafter, the noise cancellation process relating to the FF filter 414 will be
described. An audio signal generated based on audio collected by the FF-NC microphone
320-2 is input to the FF filter 414. The audio signal generated based on the audio
collected by the FF-NC microphone 320-2 and the audio signal generated based on the
audio collected by the ear canal microphone 320-3 are input to an adaptive control
unit 415. Then, the adaptive control unit 415 adaptively controls the characteristic
-α of the FF filter 414 based on these audio signals. Under the adaptive control by
the adaptive control unit 415, the FF filter 414 generates the noise cancellation
signal (second noise cancellation signal) by the noise cancellation process of the
FF scheme based on the input audio signal. The noise cancellation signal generated
by the FF filter 414 is synthesized with the noise cancellation signal generated by
the first FB filter 411 by the adder 431. The synthesized signal is amplified by the
amplifier 421 and output from the driver 310.
[0192] The case where the ear canal microphone 320-3 is used as the error microphone has
been described in detail above. As an algorithm of the adaptive control unit 415,
for example, least mean square (LMS) or filtered-X LMS can be used. There is a case
where it is desirable to use a characteristic (also referred to as a secondary path
or secondary path characteristic) from a secondary sound source to an error microphone
for the control by the adaptive control unit 415 in order to improve the noise canceling
performance. The secondary path characteristic in the model configuration example
illustrated in FIG. 33 corresponds to ADH
1H
2, which is a characteristic from the driver 310 to the ear canal microphone 320-3.
[0193] The secondary path characteristic may be measured using a measurement signal when
the user wears the headphones, or a general measurement value measured in advance
may be used. Hereinafter, signal processing to measure the secondary path characteristic
using the measurement signal will be described with reference to FIG. 34.
[0194] FIG. 34 is a diagram illustrating a model configuration example of a secondary path
characteristic measurement process using the headphones 300 according to the present
embodiment. In the model configuration example illustrated in FIG. 34, a measurement
signal generation unit 451 and a measurement signal analysis unit 452 are added to
the model configuration example illustrated in FIG. 33. In addition, both the first
FB filter 411 and the FF filter 414 are turned off and stop operating. Hereinafter,
the measurement signal generation unit 451 and the measurement signal analysis unit
452 will be described in detail.
[0195] The measurement signal generation unit 451 generates a measurement signal. As the
measurement signal, for example, an arbitrary sequence such as a time stretched pulse
(TSP) signal, white noise, and an M-sequence signal can be used. The measurement signal
generated by the measurement signal generation unit 451 is amplified by the amplifier
421, input to the driver 310, and output as audio. The audio output from the driver
310 is collected by the ear canal microphone 320-3 via the spaces 401 and 402. Then,
the audio signal generated by the ear canal microphone 320-3 is input to the measurement
signal analysis unit 452. As described above, the audio signal input to the measurement
signal analysis unit 452 is obtained by applying the characteristic ADH
1H
2M
3 to the measurement signal. The measurement signal analysis unit 452 calculates the
secondary path characteristic ADH
1H
2 based on the measurement signal generated by the measurement signal generation unit
451, the audio signal obtained by the ear canal microphone 320-3, and the known M
3.
[0196] In this manner, the secondary path characteristic ADH
1H
2 can be measured. The adaptive control unit 415 can improve the noise canceling performance
by controlling the characteristic -α of the FF filter based on the secondary path
characteristic measured in advance by the above-described processing.
[0197] Here, the characteristics H
1 and H
2 differ for each user due to characteristics of the ear canal 5 and physical characteristics
such as a shape of the pinna 2. Therefore, when a fixed filter is used, it is desirable
to correct the filter characteristic based on the secondary path characteristic ADH
1H
2 of the individual user measured using the measurement signal. Hereinafter, this point
will be described in detail.
-Case of Correcting Fixed Filter Using Ear Canal Microphone 320-3
[0198] The ear canal microphone 320-3 may be used to correct the fixed filter of NC. Specifically,
the signal processing unit 331 measures the secondary path characteristic ADH
1H
2 by the above-described measurement process using the measurement signal generation
unit 451 and the measurement signal analysis unit 452. Then, the signal processing
unit 331 corrects a characteristic (that is, a filter coefficient) of the fixed filter
to generate the noise cancellation signal based on the measured secondary path characteristic
ADH
1H
2. The fixed filter characteristic is designed based on a general secondary path characteristic,
and individual differences among users can be absorbed by correcting the filter characteristic
based on the secondary path characteristic measured for a user wearing the headphones
300. As a result, the noise canceling performance can be improved. The fixed filter
to be corrected may be the FF filter or the FB filter. Hereinafter, an example in
which the fixed filter to be corrected is the FF filter 414 illustrated in FIG. 34
will be described.
[0199] The general secondary path characteristic measured in advance is defined as ADH
1commonH
2common. Further, the secondary path characteristic of the individual user including the
influence caused by the physical characteristics such as the characteristics of the
ear canal 5 and the shape of the pinna 2 is defined as ADH
1personalH
2personlal.
[0200] A difference characteristic between the general secondary path characteristic ADH
1CommonH
2common and the secondary path characteristic ADH
1personalH
2personlal of the individual user is defined as ΔH. ΔH is defined as follows.
[0201] FF-NC is designed so as to minimize a sound pressure at an eardrum position for a
leak signal. That is, the characteristic α of the FF filter is designed such that
the following expression is satisfied.
[0202] The fixed filter of FF-NC is designed based on a general secondary path characteristic
DH
1commonH
2common. That is, the characteristic α of the FF filter is fixedly designed as the following
formula.
[0203] When a fixed filter designed based on the general secondary path characteristics
DH
1CommonH
2common is used, the FF-NC residual caused by individual differences in physical characteristics
is expressed as the following formula by putting the filter characteristic obtained
by Formula (B14) into Formula (B13).
[0204] Here, the sound pressure at the eardrum position is minimized if the general secondary
path characteristic and the secondary path characteristic pf the individual user are
the same, that is, if ADH
1personalH
2personlal = ADH
1commonH
2common. However, there is a difference between a general next path characteristic and the
secondary path characteristic of the individual user in many cases. Therefore, the
signal processing unit 331 can personalize the filter characteristic and absorb the
individual difference by multiplying the filter characteristic of the fixed filter
by ΔH as a correction characteristic. A filter characteristic obtained by multiplying
the filter characteristic of the fixed filter by the correction characteristic ΔH
is expressed by the following formula.
[0205] As illustrated in Formula (B16), the signal processing unit 331 can absorb the individual
difference of the user by multiplying the fixed filter of FF-NC by the correction
characteristic. Therefore, it is possible to improve the noise canceling performance
as compared with a case where the fixed filter designed based on the general secondary
path characteristic is used as it is.
(3) Third Noise Cancellation Process
[0206] A third noise cancellation process is a process in which the first noise cancellation
process described above with reference to FIG. 32 and the second noise cancellation
process described above with reference to FIG. 33 are combined. That is, the third
noise cancellation process is a process using the ear canal microphone 320-3 as an
error microphone of FB-NC by the second FB filter 412 and as an error microphone for
adaptive control of FF-NC by the FF filter 414. In the third noise cancellation process,
the effects of both the first noise cancellation process and the second noise cancellation
process are achieved, and thus, a higher noise canceling effect than either one is
expected. Hereinafter, details of the third noise cancellation process will be described
with reference to FIG. 35.
[0207] FIG. 35 is a diagram illustrating a model configuration example of the third noise
cancellation process using the headphones 300 according to the present embodiment.
As illustrated in FIG. 35, the ear canal microphone 320-3 collects audio and generates
an audio signal. The audio signal is input to the second FB filter 412 via the adder
432 and is also input to the adaptive control unit 415. In this manner, the ear canal
microphone 320-3 functions as the error microphone for adaptive control of FF-NC by
the FF filter 414 while functioning as the error microphone of FB-NC by the second
FB filter 412. Detailed signal processing is the same as described above with reference
to FIGS. 32 and 33, and thus, the description thereof is omitted here.
[0208] Note that the ear canal microphone 320-3 may be used to correct a filter characteristic
of a fixed filter when the FF filter 414 is designed as the fixed filter. That is,
the ear canal microphone 320-3 may be used for the secondary path characteristic measurement
process, and a correction characteristic based on the measurement result may be applied
to the fixed filter. As a result, individual differences in the secondary path characteristics
can be absorbed, and the noise canceling performance can be improved.
(4) Fourth Noise Cancellation Process
[0209] A fourth noise cancellation process is a process of performing an internal model
control (IMC) type FB-NC using the ear canal microphone 320-3. Similar to the FF-NC,
IMC-type FB-NC is a method of maximizing a noise canceling effect by minimizing the
numerator of the sensitivity function (that is, the numerator of the coefficient relating
to the noise N in the above Formula (A3)). Hereinafter, the IMC type FB-NC will be
referred to as IMC-FB to be distinguished from FB-NC that maximizes the denominator
of the above Formula (1) using the characteristic β. In the fourth noise cancellation
process, the signal processing unit 331 generates a fourth noise cancellation signal
by the IMC-FB based on the first audio signal generated by the FB-NC microphone 320-1.
The signal processing unit 331 adaptively controls the filter characteristics of the
FB filter 413 used for this IMC-FB based on the third audio signal generated by the
ear canal microphone 320-3. According to this method, the error microphone position
of IMC-FB is close to the eardrum 9, and thus, a high noise canceling effect is expected.
Hereinafter, details of the fourth noise cancellation process will be described with
reference to FIG. 36.
[0210] FIG. 36 is a diagram illustrating a model configuration example of the fourth noise
cancellation process using the headphones 300 according to the present embodiment.
The model configuration example illustrated in FIG. 36 is different from the model
configuration example illustrated in FIG. 33 in terms of having the third FB filter
413 instead of the first FB filter 411 and having an adaptive control unit 416 which
adaptively controls the third FB filter 413. Since the noise cancellation process
relating to the FF filter 414 is the same as described above with reference to FIG.
33, the detailed description thereof is omitted here. Hereinafter, the noise cancellation
process (IMC-FB) relating to the third FB filter 413 will be described in detail.
[0211] The FB-NC microphone 320-1 collects audio and generates an audio signal. An adder
433 subtracts a signal, obtained by applying internal models (:characteristics D',
H
1', and M
1') illustrated in blocks 441, 442, and 445 to the output signal input to the driver
310, from the audio signal generated by the FB-NC microphone 320-1 to perform the
synthesis. These internal models have characteristics that simulate characteristics
from the input of the output signal to the driver 310 to the generation of the first
audio signal. The synthesized signal is input to the third FB filter 413 and input
to the adaptive control unit 416. On the other hand, the audio signal generated based
on the audio collected by the ear canal microphone 320-3 is also input to the adaptive
control unit 416. The adaptive control unit 416 adaptively controls the characteristic
β
3 of the third FB filter 413 based on these input audio signals. Under the adaptive
control by the adaptive control unit 416, the third FB filter 413 generates a noise
cancellation signal by the noise cancellation process of the FB scheme based on the
input audio signals. The noise cancellation signal generated by the third FB filter
413 is combined with the noise cancellation signal generated by the FF filter 414
by the adder 431. The synthesized signal is amplified by the amplifier 421 and output
from the driver 310.
[0212] Note that the ear canal microphone 320-3 may be used to correct a filter characteristic
of a fixed filter when the third FB filter 413 is designed as the fixed filter. That
is, the ear canal microphone 320-3 may be used for the secondary path characteristic
measurement process, and a correction characteristic based on the measurement result
may be applied to the fixed filter. As a result, individual differences in the secondary
path characteristics can be absorbed, and the noise canceling performance can be improved.
(5) Fifth Noise Cancellation Process
[0213] A fifth noise cancellation process is a process in which the first noise cancellation
process described above with reference to FIG. 32 and the fourth noise cancellation
process described above with reference to FIG. 36 are combined. That is, the fifth
noise cancellation process is a process using the ear canal microphone 320-3 as the
following three types of error microphones. Firstly, the ear canal microphone 320-3
is used as the error microphone for adaptive control of FF-NC by the adaptive control
unit 415. Secondly, the ear canal microphone 320-3 is used as the error microphone
of FB-NC by the second FB filter 412. Thirdly, the ear canal microphone 320-3 is used
as the error microphone for adaptive control of IMC-FB by the adaptive control unit
416. In the fifth noise cancellation process, the effects of both the first noise
cancellation process and the fourth noise cancellation process are achieved, and thus,
a much higher noise canceling effect than either one is expected. Hereinafter, details
of the fifth noise cancellation process will be described with reference to FIG. 37.
[0214] FIG. 37 is a diagram illustrating a model configuration example of the fifth noise
cancellation process using the headphones 300 according to the present embodiment.
As illustrated in FIG. 37, the ear canal microphone 320-3 collects audio and generates
an audio signal. This audio signal is input to the second FB filter 412 via the adder
432, input to the adaptive control unit 415, and input to the adaptive control unit
416. In this manner, the ear canal microphone 320-3 functions as the three types of
error microphones described above. Detailed signal processing is the same as described
above with reference to FIGS. 32 and 36, and thus, the description thereof is omitted
here.
(6) Supplement
[0215] Although the above description has been given based on the assumption that the headphones
300 according to the present embodiment include the three audio input units 320, the
present embodiment is not limited to such an example. The headphones 300 do not necessarily
have either the FB-NC microphone 320-1 or the FF-NC microphone 320-2 among the three
audio input units 320. When the headphones 300 do not have the FF-NC microphone 320-2,
the noise cancellation process using the FF filter 414 is omitted from the first to
fifth noise cancellation processes described above. When the headphones 300 do not
have the FB-NC microphone 320-1, the noise cancellation processes using the first
FB filter 411 and the third FB filter 413 are omitted from the first to fifth noise
cancellation processes described above. In either case, at least the position of the
error microphone is close to the eardrum 9, and thus, a high noise canceling effect
is expected.
<2.5. Details of Structure of Headphones 300>
[0216] Hereinafter, a structure of the headphones 300 according to the present embodiment
will be described in detail.
(1) Arrangement of Audio Input Unit
[0217] First, the arrangement of the audio input unit 320 included in the headphones 300
will be described with reference to FIGS. 38 and 39
[0218] FIG. 38 is a diagram for describing an example of the configuration of the headphones
300 according to the present embodiment. FIG. 38 illustrates the configuration in
the state where the headphones 300 are worn by the user. As illustrated in FIG. 38,
the headphones 300 include the housing 301 and the ear pad 302. The housing 301 is
provided with the driver 310, the FB-NC microphone 320-1, and the FF-NC microphone
320-2. In addition, the ear canal microphone 320-3 is arranged at a position away
from the housing 301 as illustrated in FIG. 38. The configuration of each of these
constituent elements is the same as described above with reference to FIG. 28 and
the like.
[0219] As described above, the headphones 300 do not necessarily include either the FB-NC
microphone 320-1 or the FF-NC microphone 320-2. FIG. 39 illustrates an example of
a configuration of headphones 300A that do not include the FF-NC microphone 320-2
but include the FB-NC microphone 320-1 and the ear canal microphone 320-3. FIG. 40
illustrates an example of a configuration of headphones 300B that do not have the
FB-NC microphone 320-1 but have the FF-NC microphone 320-2 and the ear canal microphone
320-3.
(2) Shape of Holding Unit
[0220] Hereinafter, variations of the shape of the holding unit 303 will be described with
reference to FIGS. 41 to 46.
[0221] FIG. 41 is a view illustrating an example of the configuration of the holding unit
303 of the headphones 300 according to the present embodiment. As illustrated in FIG.
41, the holding unit 303 may be a ring-shaped structure that forms a circle. The ear
canal microphone 320-3 is provided at a distal end of the rod-shaped first support
member 305 provided in a ring inner direction of the holding unit 303, and all the
other parts of the ring-shaped structure are the opening portions 304.
[0222] FIG. 42 is a view illustrating an example of the configuration of the holding unit
303 of the headphones 300 according to the present embodiment. As illustrated in FIG.
42, the holding unit 303 may be a ring-shaped structure that forms an ellipse. The
ear canal microphone 320-3 is provided at a distal end of the rod-shaped first support
member 305 provided in a ring inner direction of the holding unit 303, and all the
other parts of the ring-shaped structure are the opening portions 304.
[0223] FIG. 43 is a view illustrating an example of the configuration of the holding unit
303 of the headphones 300 according to the present embodiment. As illustrated in FIG.
43, the holding unit 303 may be a structure in which each side of a triangle is formed
of a rod-shaped structure. The ear canal microphone 320-3 is provided at a distal
end of the rod-shaped first support member 305 provided in a triangle inner direction
of the holding unit 303, and all the other parts of the triangle-shaped structure
are the opening portions 304.
[0224] FIG. 44 is a view illustrating an example of the configuration of the holding unit
303 of the headphones 300 according to the present embodiment. As illustrated in FIG.
44, the holding unit 303 may be a structure in which a holding unit 303A configured
using a ring-shaped structure forming a circle and a holding unit 303B configured
using a ring-shaped structure forming an ellipse are connected. The ear canal microphone
320-3 is provided at a distal end of the rod-shaped first support member 305 provided
in a ring inner direction of the holding unit 303A, and all the other parts of the
ring-shaped structure are the opening portions 304.
[0225] In the example illustrated in FIGS. 41 to 44, the holding unit 303 has the opening
portion 304. On the other hand, the holding unit 303 does not necessarily have the
opening portion 304 as illustrated in FIGS. 45 and 46.
[0226] FIG. 45 is a view illustrating an example of the configuration of the holding unit
303 of the headphones 300 according to the present embodiment. As illustrated in FIG.
45, the holding unit 303 may be a sponge-shaped structure that forms a circle. The
ear canal microphone 320-3 is provided at the center of the holding unit 303.
[0227] FIG. 46 is a view illustrating an example of the configuration of the holding unit
303 of the headphones 300 according to the present embodiment. As illustrated in FIG.
46, the holding unit 303 may be an umbrella-shaped structure that has a narrow outer
diameter in an insertion direction (X-axis negative direction) into the ear canal
5 and a wide outer diameter on the opposite side (X-axis positive direction). The
ear canal microphone 320-3 is provided at the center of the holding unit 303.
[0228] The examples of the shape of the holding unit 303 have been described above. Note
that the holding unit 303 can be formed using an elastic body such as rubber, silicon,
and sponge.
[0229] It is desirable that the ear canal microphone 320-3 be arranged at the same position
as the microphone 141 which has been described in the first embodiment with reference
to FIG. 6 and the like. That is, it is desirable that the ear canal microphone 320-3
be arranged in a space 15 mm away from the boundary 19 of the cavum concha 4 and the
ear canal 5 to the eardrum 9 side or arranged in a space 15 mm away from the boundary
19 of the cavum concha 4 and the ear canal 5 on the opposite side of the eardrum 9.
In other words, it is desirable that the holding unit 303 hold the ear canal microphone
320-3 in the space 15 mm away from the boundary 19 of the cavum concha 4 and the ear
canal 5 to the eardrum 9 side or in the space 15 mm away from the boundary 19 of the
cavum concha 4 and the ear canal 5 on the opposite side of the eardrum 9 in a state
where the headphones 300 are worn by the user. Here, a difference between the frequency
characteristic at the position of the ear canal microphone 320-3 and the frequency
characteristic at the position of the eardrum 9 decreases as the ear canal microphone
320-3 approaches the eardrum 9. Therefore, it is more desirable if the position of
the ear canal microphone 320-3 is closer to the eardrum 9. In this regard, the above
difference between the frequency characteristics can fall within an allowable range
if the space 15 mm away from the boundary 19 to the opposite side of the eardrum 9,
and the predetermined noise canceling performance can be ensured. In addition, when
the ear canal microphone 320-3 is arranged in the range within 15 mm away from the
boundary 19 to the eardrum 9 side, the position of the microphone 141 can be made
closer to the eardrum 9 as compared with the case where the microphone 141 is arranged
in the space on the opposite side of the eardrum 9 from the boundary 19. Further,
at least the microphone 141 can be prevented from coming into contact with the eardrum
9 and damaging the eardrum 9, and the safety can be ensured.
(3) Wired Connection Unit
[0230] Next, the connection between the housing 301 and the ear canal microphone 320-3 will
be described with reference to FIGS. 47 to 49.
[0231] FIG. 47 is a diagram illustrating an example of the configuration of the headphones
300 according to the present embodiment. FIG. 48 is a view illustrating the configuration
of the headphones 300 illustrated in FIG. 47 as viewed from another viewpoint. In
the example illustrated in FIG. 47, the headphones 300 include a wired connection
unit 340. The wired connection unit 340 connects the housing 301 and the ear canal
microphone 320-3 in a wired manner. More specifically, the wired connection unit 340
connects the signal processing unit 331 stored in the housing 301 and the ear canal
microphone 320-3 in a wired manner. The wired connection unit 340 is formed using
a member capable of transmitting a signal, such as an electric wire and an optical
fiber.
[0232] Further, the headphones 300 include a winding unit 341 that winds up the wired connection
unit 340. For example, the winding unit 341 includes: a winding core portion around
which the wired connection unit 340 is wound; a support portion which rotatably supports
the winding core portion; and a drive unit that rotates the winding core portion in
a direction in which the wired connection unit 340 is wound up. The drive unit includes
a spring, a motor, or the like, and drives the wired connection unit 340 sent out
from the winding core portion so as to be wound around the winding core portion. As
a result, it is possible to prevent the wired connection unit 340 from being left
in the inner space 30 excessively. Accordingly, tangling of the wired connection unit
340 is prevented. In addition, when the user wears the headphones 300, the wired connection
unit 340 can be prevented from being pinched between the ear pad 302 and the user's
head.
[0233] The winding unit 341 may include a stopper mechanism that changes the winding amount
of the wired connection unit 340 in accordance with a user, a device that controls
the rotation of the drive unit, and the like. Although the optimum winding amount
can vary depending on a size of user's ear and the like, this configuration can optimize
the winding amount.
[0234] The wired connection unit 340 is sent out freely from the winding unit 341. The user
can wear the headphones 300 while winding the wired connection unit 340 around the
winding unit 341 after wearing the holding unit 303 by pulling out the wired connection
unit 340 before wearing the headphones 300.
[0235] FIG. 49 is a diagram illustrating an example of the configuration of the headphones
300 according to the present embodiment. As illustrated in FIG. 49, the housing 301
may include a recess 342 that can accommodate at least a part of the holding unit
303 and the ear canal microphone 320-3 on the inner space 30 side. The recess 342
is formed in the wall portion 301a on the inner space 30 side of the housing 301.
For example, the recess 342 has a groove having a shape that matches the shapes of
the holding unit 303 and the ear canal microphone 320-3, and the holding unit 303
and the ear canal microphone 320-3 are accommodated in the groove in the non-wearing
state. Note that the recess 342 may be provided in the ear pad 302.
(4) Second Support Member
[0236] The headphones 300 can include the second support member 306 as described above with
reference to FIG. 28 and the like. Hereinafter, a configuration of the second support
member 306 will be described with reference to FIGS. 50 to 62.
[0237] FIG. 50 is a diagram illustrating an example of the configuration of the headphones
300 according to the present embodiment. FIGS. 51 to 53 are views illustrating the
configuration of the headphones 300 illustrated in FIG. 50 as viewed from other viewpoints.
In the example illustrated in FIG. 50, the headphones 300 include the second support
member 306 having one end 306a connected to the housing 301 and another end 306b connected
to the holding unit 303. As illustrated in FIG. 50, the second support member 306
may be a rod-shaped structure curved in an S shape. The second support member 306
is formed using an elastic body such as silicon and rubber so as to protrude from
the housing 301 to the user's ear side. As a result, the second support member 306
fixes the holding unit 303 to be gently pressed near the entrance of the user's ear
canal 5 while following a shape and a size of the ear and a size of the head of the
user when the headphones 300 are worn by the user. In addition, the second support
member 306 may be formed using a thermoplastic resin, and in this case, the holding
unit 303 can be prevented from being excessively pressed against the user's ear.
[0238] FIG. 54 is a diagram illustrating a configuration when the headphones 300 illustrated
in FIG. 50 are not worn. As illustrated in FIG. 54, the holding unit 303 protrudes
outward beyond the contact surface 302a between the ear pad 302 and the user's head.
As a result, the second support member 306 is elastically deformed, and the holding
unit 303 is pressed against the user's ear by the stress caused by the elastic deformation
when the headphones 300 are worn by the user. A length of the holding unit 303 protruding
beyond the contact surface 302a is desirably 30 mm or less. As a result, it is possible
to prevent the holding unit 303 from being excessively pressed against the user's
ear. In addition, the holding unit 303 can be prevented from being excessively inserted
into the user's ear canal 5.
[0239] FIG. 55 is a diagram illustrating an example of the configuration of the headphones
300 according to the present embodiment. In the example illustrated in FIG. 55, the
wired connection unit 340 is stored inside the second support member 306. In this
case, the wired connection unit 340 is not exposed in the inner space 30, and thus,
the time and effort for pulling out or winding the wired connection unit 340 from
or around the winding unit 341 is omitted so that the convenience for the user is
improved.
[0240] FIG. 56 is a diagram illustrating an example of the configuration of the headphones
300 according to the present embodiment. FIGS. 57 to 59 are views illustrating the
configuration of the headphones 300 illustrated in FIG. 56 as viewed from other viewpoints.
In the example illustrated in FIG. 56, the headphones 300 include a plurality of second
support members 306A to 306C. One ends 306Aa to 306Ca of the second support members
306A to 306C are connected to the housing 301 at different positions. The other ends
306Ab to 306Cb of the second support members 306A to 306C are connected to the holding
unit 303 at different positions. With this configuration, a relative positional relationship
between the ear canal microphone 320-3 and the driver 310 is hardly changed every
time the headphones 300 are worn. Since the relative positional relationship is constant,
it is unnecessary to update a noise canceling filter every time the headphones 300
are worn, or the update amount can be suppressed. In addition, this configuration
makes it difficult for the ear canal microphone 320-3 to be displaced from the ear
hole during wearing of the headphones 300. As a result, the noise cancellation process
during wearing of the headphones 300 can be stabilized.
[0241] FIG. 60 is a diagram illustrating an example of the configuration of the headphones
300 according to the present embodiment. FIG. 61 is a view illustrating the configuration
of the headphones 300 illustrated in FIG. 60 as viewed from another viewpoint. In
the example illustrated in FIG. 60, the second support member 306 has a link structure.
Specifically, the second support member 306 includes links 350a and 350b and a joint
portion 351 that movably connects the links 350a and 350b. The link 350 may be formed
using an elastic body or may be formed using an elastoplastic body or a plastic body
such as plastic, metal, and wood. The second support member 306 may have one degree
of freedom or a plurality of degrees of freedom. For example, the second support member
306 may have three or more links 350. In addition, the joint portion 351 may be a
pin that connects the respective links 350 so as to be rotatable with one degree of
freedom, or may be a ball and a socket that connects the respective links 350 with
two or more degrees of freedom. Since the second support member 306 having the link
structure with the high degree of freedom is used, the holding unit 303 can be fitted
to users having various ear shapes.
[0242] In addition, each of the links 350a and 350b is connected by a restraining member
352, and a movable range is restrained within a predetermined range when referring
to FIG. 60. For example, the restraining member 352 is formed using an elastic body
such as rubber and a spring. The restraining member 352 can restrain a direction in
which the holding unit 303 and the ear canal microphone 320-3 face to a predetermined
range by restraining the movable range of the link 350 to the predetermined range.
For example, the restraining member 352 can restrain the direction in which the holding
unit 303 and the ear canal microphone 320-3 face to a direction of the user's ear.
[0243] In addition, the second support member 306 may have a slide mechanism. When referring
to FIG. 61, the one end 306a of the second support member 306 is connected to a sliding
member 353 that slides on the wall portion 301a of the housing 301. The sliding member
353 is engaged with a rail 354 provided on the wall portion 301a of the inner space
30 and slides. The rail 354 is a groove-shaped structure, for example, and is formed
so as to partially surround the driver 310. Since the second support member 306 has
the slide mechanism, the movable range of the holding unit 303 and the ear canal microphone
320-3 are widened, and thus, the holding unit 303 can be fitted to users having various
ear shapes.
[0244] Note that the movable range of the holding unit 303 and the ear canal microphone
320-3 is desirably limited within 40 mm or less in the longitudinal direction of the
user's head (substantially the Y-axis direction) and within 70 mm or less in the vertical
direction of the user's head (substantially the Z-axis direction) inside a plane parallel
to the contact surface 302a as illustrated in FIG. 61. This restriction is realized
by, for example, the length of the link 350, the movable range of the joint portion
351, the arrangement of the rail 354, and the like. Due to the limitation of the movable
range, the movable range of the holding unit 303 and the ear canal microphone 320-3
can be limited to a range that enables fitting to the user's ear.
[0245] FIGS. 62 and 63 are views illustrating examples of the configuration of the headphones
300 according to the present embodiment. In the example illustrated in FIG. 62, the
headphones 300 include second support members 306A and 306B having a link structure.
In the example illustrated in FIG. 63, the headphones 300 include second support members
306A, 306B, and 306C having a link structure. The second support member 306A is connected
to a sliding member 353A that slides on a rail 354A. The second support member 306B
is connected to a sliding member 353B that slides on a rail 354B. The second support
member 306C is connected to a sliding member 353C that slides on a rail 354C. As described
above, the headphones 300 may include the plurality of second support members 306
having the link structure. With this configuration, a relative positional relationship
between the ear canal microphone 320-3 and the driver 310 is hardly changed every
time the headphones 300 are worn. Since the relative positional relationship is constant,
it is unnecessary to update a noise canceling filter every time the headphones 300
are worn, or the update amount can be suppressed. In addition, this configuration
makes it difficult for the ear canal microphone 320-3 to be displaced from the ear
hole during wearing of the headphones 300. As a result, the effect of the noise cancellation
process during wearing of the headphones 300 can be stabilized.
[0246] FIG. 64 is a diagram illustrating an example of the configuration of the headphones
300 according to the present embodiment. In the example illustrated in FIG. 64, the
headphones 300 include an attitude control device 360 that controls an attitude of
the second support member 306. The attitude control device 360 includes an operating
body 361, a link 362, and a joint portion 363. The link 362 is arranged through a
through-hole that penetrates the housing 301 from the inner space 30 to the outer
space 31. One end of the link 362 protruding into the inner space 30 is movably connected
to the second support member 306 by the joint portion 363. The other end of the link
362 on the outer space 31 side is connected to the operating body 361. The operating
body 361 is at least partially exposed to the outer space 31 and is movably arranged.
When the operating body 361 is moved, the movement is transmitted to the second support
member 306 via the link 362 and the joint portion 363. The user can move or deform
the attitude of the second support member 306 by pinching the operating body 361 and
moving the operating body 361 in three axial direction. Accordingly, the user can
move the second support member 306 while wearing the headphones 300, that is, without
putting the hand into the inner space 30. In addition, even if the holding unit 303,
the ear canal microphone 320-3, or the second support member 306 is caught on the
ear at the time of wearing or removing the headphones 300, the user can easily resolve
the catching by operating the attitude control device 360. Accordingly, the member
caught by the user can be prevented from being damaged or the user can be prevented
from being injured. The attitude control device 360 may include power such as a motor,
and may control the attitude of the second support member 306 using such power. For
example, the attitude control device 360 automatically controls the attitude of the
second support member 306 when detecting wearing or removal of the headphones 300.
<2.6. Control in Response to Wearing/Non-Wearing of Headphones 300>
[0247] The operation control unit 333 determines wearing/non-wearing of the headphones 300.
[0248] For example, in the example illustrated in FIG. 49, the operation control unit 333
determines the wearing/non-wearing of the headphones 300 based on whether the holding
unit 303 and the ear canal microphone 320-3 are accommodated in the recess 342. For
example, the operation control unit 333 determines that the headphones 300 are worn
when the holding unit 303 and the ear canal microphone 320-3 are not accommodated
in the recess 342. In addition, the operation control unit 333 determines that the
headphones 300 are not worn when the holding unit 303 and the ear canal microphone
320-3 are accommodated in the recess 342. Note that a sensor or a switch that detects
whether the holding unit 303 and the ear canal microphone 320-3 are accommodated in
the recess 342 may be provided in the recess 342 or the winding unit 341.
[0249] In addition, the operation control unit 333 may determine the wearing/non-wearing
of the headphones 300 based on whether the deformation of the second support member
306 has been detected in the example illustrated in FIG. 50. In addition, the operation
control unit 333 may determine the wearing/non-wearing of the headphones 300 based
on whether there has been user's operation input to the attitude control device 360,
whether the deformation of the ear pad 302 has been detected, and the like in the
example illustrated in FIG. 64.
[0250] Then, the operation control unit 333 controls the operation of the headphones 300
based on the result of the determination on the wearing/non-wearing of the headphones
300. For example, the operation control unit 333 may cause the signal processing unit
331 to start generating a noise cancellation signal when determining that the headphones
300 are worn. In addition, the operation control unit 333 may cause the driver 310
to start outputting an output signal when determining that the headphones 300 are
worn. As a result, the operation of the ear hole opening device 100 is automatically
started when the user wears the headphones 300, and thus, an operation burden on the
user is reduced. In addition, when determining that the headphones 300 are not worn,
the operation control unit 333 may stop the generation of the noise cancellation signal
and the output of the output signal. As a result, the operation of the headphones
300 is automatically stopped or partly stopped in the non-wearing state, and thus,
wasteful power consumption can be prevented.
<2.7. Summary>
[0251] The second embodiment has been described in detail above. As described above, the
headphones 300 according to the second embodiment include the FB-NC microphone 320-1,
the FF-NC microphone 320-2, and the ear canal microphone 320-3, and perform the noise
cancellation process based on the audio signals generated by these microphones. When
the ear canal microphone 320-3 is used as the error microphone of FB-NC, the cancellation
point of FB-NC is close to the eardrum 9, and thus, the high noise canceling effect
is expected. Further, when the FB-NC microphone 320-1 is used together as the error
microphone of FB-NC, both the first and second guidelines can be satisfied. That is,
it is possible to minimize the sound pressure at the cancellation point close to the
eardrum position while suppressing the distance delay.
[0252] In addition, the ear canal microphone 320-3 may be used as the error microphone for
adaptive processing in FF-NC or IMC-FB. In either case, the error microphone is arranged
near the eardrum 9, and thus, the improvement of the noise canceling performance is
expected.
[0253] In addition, the ear canal microphone 320-3 may be used in the measurement processing
for calculation of the correction characteristic of the fixed filter. In this case,
since individual differences caused by the physical characteristics of the users wearing
the headphones 300 can be absorbed, the noise canceling performance can be improved
as compared with the case where the noise cancellation process is performed using
the fixed filter as it is.
<<3. Third Embodiment>>
[0254] A third embodiment is a mode of realizing the noise cancellation process described
in the second embodiment by cooperation of a first audio processing device and a second
audio processing device. For example, the first audio processing device may be an
earphone such as the ear hole opening device 100 described in the first embodiment.
In addition, the second audio processing device may be headphones 500 to be described
below. Note that the two audio processing devices that cooperate with each other are
not limited to the combination of the earphone and the headphones as long as devices
can be worn in the state of partially or entirely overlapping each other.
<3.1. Basic Configuration of Ear Hole Opening Device>
[0255] First, a basic configuration of the ear hole opening device 100 according to the
present embodiment will be described with reference to FIGS. 65 and 66.
[0256] FIG. 65 is a diagram illustrating an example of an internal configuration of the
ear hole opening device 100 according to the present embodiment. As illustrated in
FIG. 65, the ear hole opening device 100 includes the driver 110, the audio information
acquisition unit 140, the control unit 150, a sensor unit 160, and the wireless communication
unit 170.
[0257] The configuration of the driver 110 is the same as described above in the first embodiment.
[0258] The configuration of the audio information acquisition unit 140 is the same as described
above in the first embodiment.
[0259] The control unit 150 includes the signal processing unit 151 and the operation control
unit 153 described above in the first embodiment, and includes a communication control
unit 157 instead of the authentication unit 155. The configurations of the signal
processing unit 151 and the operation control unit 153 are the same as described above
in the first embodiment. The communication control unit 157 has a function of controlling
wireless communication processing performed by the wireless communication unit 170.
Specifically, the communication control unit 157 controls communication partner selection
and communication data transmission/reception processing. The control unit 150 according
to the present embodiment may include the authentication unit 155.
[0260] The sensor unit 160 is a device that detects information on the ear hole opening
device 100, information on a user wearing the ear hole opening device 100, or information
on the headphones 500 that are worn to overlap the ear hole opening device 100. The
sensor unit 160 can include various sensor devices such as a pressure-sensitive sensor,
a gyro sensor, an acceleration sensor, and a body temperature sensor. In addition,
the sensor unit 160 may include a magnetic sensor. In addition, the sensor unit 160
may include an RFID device such as a radio frequency identifier (RFID) tag and a reader.
[0261] The wireless communication unit 170 is an interface for wireless communication between
the ear hole opening device 100 and the headphones 500. The wireless communication
unit 170 can perform wireless communication by an arbitrary scheme. For example, the
wireless communication unit 170 may perform wireless communication by optical communication.
The optical communication can realize an ultra-low delay. In addition, the wireless
communication unit 170 may perform wireless communication using an analog method similar
to radio broadcasting such as frequency modulation (FM) and amplitude modulation (AM).
These analog methods can also realize a low delay. In addition, the wireless communication
unit 170 may perform wireless communication conforming to Wi-Fi (registered trademark),
Bluetooth (registered trademark), or a so-called 2.4 GHz band wireless communication
standard such as BLE (Bluetooth Low Energy (registered trademark)). In addition, the
wireless communication unit 170 may perform wireless communication by a method using
magnetic resonance, such as near field magnetic induction (NFMI). Of course, a communication
scheme, a band, and a modulation scheme are not limited to the above examples.
[0262] The internal configuration of the ear hole opening device 100 has been described
above. Next, an exterior configuration and basic internal processing of the ear hole
opening device 100 will be described with reference to FIG. 66.
[0263] FIG. 66 is a diagram for describing an outline of the ear hole opening device 100
according to the present embodiment. The drawing in the upper part of FIG. 66 illustrates
the exterior configuration of the ear hole opening device 100. As illustrated in the
upper part of FIG. 66, the ear hole opening device 100 has the exterior configuration
which is the same as described above in the first embodiment. The present embodiment
will be described on the assumption that the microphone 141 is used as the audio information
acquisition unit 140, but the eardrum sound pressure acquisition unit 142 may be used
as the audio information acquisition unit 140.
[0264] The lower part of FIG. 66 illustrates the outline of the internal processing when
the ear hole opening device 100 operates alone. An audio signal generated by the microphone
141 is input to a FB filter 601. The FB filter 601 performs a noise cancellation process
of a FB scheme based on the input audio signal to generate a noise cancellation signal,
and outputs the noise cancellation signal to the driver 110. The driver 110 outputs
audio based on the input noise cancellation signal. In this manner, the noise cancellation
process of the FB scheme using the microphone 141 as a cancellation point is performed.
[0265] Detailed signal processing is the same as described above with reference to FIG.
8. The FB filter 601 corresponds to the first FB filter 201. Specifically, the FB
filter 601 performs the noise cancellation process of the FB scheme using the microphone
141 as the cancellation point.
<3.2. Basic Configuration of Headphones 500>
[0266] Subsequently, a basic configuration of the headphones 500 according to the present
embodiment will be described with reference to FIGS. 67 and 68.
[0267] FIG. 67 is a diagram illustrating an example of an internal configuration of the
headphones 500 according to the present embodiment. As illustrated in FIG. 67, the
headphones 500 include an audio output unit 510, an audio input unit 520, a control
unit 530, a sensor unit 540, and a wireless communication unit 550.
• Audio Output Unit 510
[0268] The audio output unit 510 (driver) has a function of outputting audio based on an
audio signal. For example, the driver 510 outputs audio to a space based on an output
signal output from a signal processing unit 531.
• Audio Input Unit 520
[0269] The audio input unit 520 includes a microphone (hereinafter also simply referred
to as a microphone) that detects ambient sounds and generates an audio signal indicating
the detection result by the microphone.
• Control Unit 530
[0270] The control unit 530 functions as an arithmetic processing device and a control device,
and controls the entire processing performed by the headphones 500 according to various
programs. The control unit 530 is realized by an electronic circuit, for example,
a central processing unit (CPU), a micro-processing unit (MPU), a demand-side platform
(DSP), or the like. Note that the control unit 530 may include a read-only memory
(ROM) that stores programs to be used, calculation parameters, and the like, and a
random-access memory (RAM) that temporarily stores parameters that change as appropriate.
Typically, the control unit 530 is stored in the housing.
[0271] As illustrated in FIG. 67, the control unit 530 includes the signal processing unit
531, an operation control unit 533, and a communication control unit 535.
[0272] The signal processing unit 531 has a function of generating a noise cancellation
signal for noise based on the audio signal generated by the audio input unit 520 and
the audio signal received from the ear hole opening device 100 by the wireless communication
unit 550. The signal processing unit 531 can generate a plurality of noise cancellation
signals. For example, the signal processing unit 531 performs at least one of the
noise cancellation process of the FB scheme and the noise cancellation process of
the FF scheme to generate the plurality of noise cancellation signals. The signal
processing unit 531 generates an audio signal (hereinafter also referred to as an
output signal) based on the plurality of generated noise cancellation signals, and
outputs the audio signal to the driver 510. For example, the output signal may be
a signal obtained by synthesizing the plurality of noise cancellation signals, or
may be a synthesized signal obtained by synthesizing another audio signal such as
a music signal acquired from a sound source and the noise cancellation signal. The
signal processing unit 531 includes various constituent elements for noise cancellation
processes which will be described with reference to FIGS. 68 to 74 and the like. For
example, the signal processing unit 531 includes: various filter circuits configured
to generate a noise cancellation signal; an adaptive control unit configured to adaptively
control the filter circuits; an adder configured to synthesize signals; and the like.
In addition, the signal processing unit 531 also includes circuits such as an amplifier,
an ADC, and a DAC.
[0273] The operation control unit 533 has a function of controlling an operation mode of
the headphones 500. The operation control unit 533 stops or activates some or all
of functions of the headphones 500. For example, the operation control unit 533 controls
the stop/activation of the function of the headphones 500 based on a detection result
obtained by the sensor unit 540.
• Sensor Unit 540
[0274] The sensor unit 540 is a device that detects information on the headphones 500, information
on a user wearing the headphones 500, or information on the ear hole opening device
100 that is worn to overlap the headphones 500. The sensor unit 540 can include various
sensor devices such as a pressure-sensitive sensor, a gyro sensor, an acceleration
sensor, and a body temperature sensor. In addition, the sensor unit 540 may include
a magnetic sensor or an RFID device such as a radio frequency identifier (RFID) tag
and a reader.
• Wireless Communication Unit 550
[0275] The wireless communication unit 550 is an interface for wireless communication between
the headphones 500 and the ear hole opening device 100. The wireless communication
unit 550 can perform wireless communication by an arbitrary scheme. For example, the
wireless communication unit 550 may perform wireless communication by optical communication.
The optical communication can realize an ultra-low delay. In addition, the wireless
communication unit 550 may perform wireless communication using an analog method similar
to radio broadcasting such as frequency modulation (FM) and amplitude modulation (AM).
These analog methods can also realize a low delay. In addition, the wireless communication
unit 550 may perform wireless communication conforming to Wi-Fi (registered trademark),
Bluetooth (registered trademark), or a so-called 2.4 GHz band wireless communication
standard such as BLE (Bluetooth Low Energy (registered trademark)). In addition, the
wireless communication unit 550 may perform wireless communication by a method using
magnetic resonance, such as near field magnetic induction (NFMI). Of course, a communication
scheme, a band, and a modulation scheme are not limited to the above examples.
[0276] The internal configuration of the headphones 500 has been described above. Next,
an exterior configuration and basic internal processing of the headphones 500 will
be described with reference to FIG. 68.
[0277] FIG. 68 is a diagram for describing an outline of the headphones 500 according to
the present embodiment. The drawing in the upper part of FIG. 68 illustrates the exterior
configuration of the headphones 500. As illustrated in the upper part of FIG. 68,
the headphones 500 have a configuration in which the ear canal microphone 320-3 is
removed from the headphones 300 described above in the second embodiment. This will
be described in detail hereinafter.
[0278] As illustrated in the upper part of FIG. 68, the headphones 500 include a housing
501 and an ear pad 502. One ear of the user wearing the headphones 500 is covered
(typically sealed) by the housing 501 and the ear pad 502. The housing 501 stores
various devices configured for signal processing such as the driver 510, audio input
units 520-1 and 520-2, and a filter circuit. The ear pad 502 comes into contact with
user's head at a contact surface 502a. The ear pad 502 is formed using an elastic
body such as sponge, and is in close contact with the user's head while being deformed
in accordance with the user's head, and forms the inner space 30. The inner space
30 is a space formed by the housing 501, the ear pad 502, and the user's head. The
inner space 30 may be a sealed space isolated from an outer space 31 that is a space
on the outside or may be connected to the outer space 31. Noise after passive sound
insulation by passive sound insulation elements, such as the housing 501, the ear
pad 502, and the user's head, arrives at the inner space 30. A wall portion 501a of
the housing 501 is in contact with the inner space 30, and an outer wall portion 501b
of the housing 501 is in contact with the outer space 31.
[0279] The driver 510 outputs audio to a space based on the audio signal. The driver 510
is provided in the housing 501. Then, the driver 510 outputs audio toward the inner
space 30 that is a space closer to the eardrum than the housing 501. For example,
the driver 510 outputs audio to the space based on the noise cancellation signal.
As a result, the noise that has arrived at the inner space 30 can be canceled.
[0280] The audio input units 520 (520-1 and 520-2) collect ambient sounds and generate audio
signals. As illustrated in FIG. 68, the two audio input units 520 are arranged on
one ear side of the user in the state of being worn by the user.
[0281] The audio input unit 520-1 is a microphone that performs sound collection for FB-NC
(that is, the FB-NC microphone). The FB-NC microphone 520-1 is arranged at a position
where a distance from the eardrum 9 of the user is shorter than the audio input unit
320-2 in a state where the headphones 500 are worn by the user. More specifically,
the FB-NC microphone 520-1 is arranged at a position where noise is collected through
shielding objects, that is, after being subjected to passive sound insulation in the
state where the headphones 500 are worn by the user. Further, it is desirable that
the FB-NC microphone 520-1 be arranged between the eardrum 9 of the user and the driver
510. The shielding objects herein are passive sound insulation elements and correspond
to the housing 501, the ear pad 502, and the user's head. As illustrated in FIG. 68,
the FB-NC microphone 520-1 is provided on the wall portion 501a of the housing 501
on the inner space 30 side. Then, the FB-NC microphone 520-1 collects audio of the
inner space 30 and generates an audio signal. The audio collected at this time contains
noise after passive sound insulation by the passive sound insulation elements. The
FB-NC microphone 520-1 corresponds to a first audio input unit, and the audio signal
generated by the FB-NC microphone 520-1 can also be referred to as a first audio signal.
The audio signal generated by the FB-NC microphone 520-1 is input to the FB filter
and used to generate the noise cancellation signal.
[0282] The audio input unit 520-2 is a microphone that performs sound collection for FF-NC
(that is, the FF-NC microphone). In addition, the FF-NC microphone 520-2 is arranged
at a position where the distance from the eardrum 9 of the user is longer than the
FB-NC microphone 520-1 in the state where the headphones 500 are worn by the user.
More specifically, the FF-NC microphone 520-2 is arranged at a position where noise
is collected without passing through shielding objects, that is, without being subjected
to passive sound insulation in the state where the headphones 500 are worn by the
user. As illustrated in FIG. 68, the FF-NC microphone 520-2 is provided on the wall
portion 501b of the housing 501 on the outer space 31 side. Then, the FF-NC microphone
520-2 collects audio of the outer space 31 and generates an audio signal. The audio
collected at this time contains noise that has arrived at the outer space 31. The
FF microphone 520-2 corresponds to a second audio input unit, and the audio signal
generated by the FF microphone 520-2 can also be referred to as a second audio signal.
Here, the FF-NC microphone 520-2 may be exposed to the outer space 31 or is not necessarily
exposed. For example, the FF-NC microphone 520-2 may be embedded in the housing 501
and may collect a wrap-around sound or a sound transmitted through a cover such as
a cloth. The audio signal generated by the FF-NC microphone 520-2 is input to the
FF filter and used to generate the noise cancellation signal.
[0283] Note that FIG. 68 illustrate an exterior configuration on the right ear side of the
headphones 500, an exterior configuration on the left ear side is bilaterally symmetric
with the exterior configuration on the right ear side. The headphones 500 may be configured
to be separated and independent from each other between the right ear side and the
left ear side, or may be integrally configured. In addition, the headphones 500 can
have an arbitrary structure such as an overhead type, a neckband type, and an ear
hook type.
[0284] The exterior configuration of the headphones 500 has been described above. Subsequently,
the internal processing when headphones 500 operate alone will be described with reference
to FIG. 68.
[0285] The lower part of FIG. 68 illustrates an outline of internal processing when the
headphones 500 operate alone. The audio signal generated by the FB-NC microphone 520-1
is input to a FB filter 701. The FB filter 701 performs a noise cancellation process
of an FB scheme using the FB-NC microphone 520-1 as a cancellation point based on
the input audio signal and generates a noise cancellation signal. The generated noise
cancellation signal is input to an adder 703. On the other hand, an audio signal generated
by the FF-NC microphone 520-2 is input to a FF filter 702. The FF filter 702 performs
a noise cancellation process of a FF scheme based on the input audio signal and generates
a noise cancellation signal. The generated noise cancellation signal is input to an
adder 703. The adder 703 synthesizes the noise cancellation signals input from the
FB filter 701 and the FF filter 702, and outputs the synthesized signal to the driver
110. The driver 110 outputs audio based on the input synthesized signal. In this manner,
the combination-type noise cancellation process is performed.
[0286] Detailed signal processing is the same as described above with reference to FIG.
27. Specifically, the FB filter 701 corresponds to the FB filter 385, and the FF filter
702 corresponds to the FF filter 387.
<3.3. Details of Noise Cancellation Process>
[0287] The user can additionally wear the headphones 500 while wearing the ear hole opening
device 100. In this case, a noise canceling effect can be improved as compared with
a case where either one of the ear hole opening device 100 or the headphones 500 is
used alone. Hereinafter, the noise cancellation process when the ear hole opening
device 100 and the headphones 500 are used in combination will be described with reference
to FIGS. 69 to 74.
(1) First Combination Example
[0288] A first combination example is an example in which the ear hole opening device 100
and the headphones 500 perform noise cancellation processes independently of each
other. This example will be described with reference to FIG. 69.
[0289] FIG. 69 is a diagram for describing the first combination example of the ear hole
opening device 100 and the headphones 500 according to the present embodiment. As
illustrated in FIG. 69, the ear hole opening device 100 and the headphones 500 are
worn in an overlapping manner. Specifically, the ear hole opening device 100 is worn
to overlap the inner side (the user's ear side, that is, the X-axis positive direction)
of the headphones 500 worn by the user. The headphones 500 are worn to overlap the
outer side (the opposite side to the user's ear, that is, in the X-axis negative direction)
of the ear hole opening device 100 worn by the user. The wearing of the headphones
500 and the ear hole opening device 100 in the overlapping manner indicates that at
least the microphone 141 of the ear hole opening device 100 is included in the inner
space 30 of the headphones 500. The inner space 30 of the headphones 500 may include
the entire ear hole opening device 100 or only a part thereof.
[0290] Here, the ear hole opening device 100 and the headphones 500 do not communicate with
each other in this example. That is, each of the noise cancellation processes described
above with reference to FIGS. 66 and 68 is performed independently. In this case,
noise that has not been canceled by the noise cancellation process described above
with reference to FIG. 68 is canceled by the noise cancellation process described
above with reference to FIG. 66. Therefore, the noise canceling effect can be improved
as compared with a case where either one of the ear hole opening device 100 or the
headphones 500 is used alone.
[0291] As described above, the noise canceling effect is improved even when the ear hole
opening device 100 and the headphones 500 operate independently. However, the noise
canceling effect can be further improved as the ear hole opening device 100 and the
headphones 500 operate in cooperation. Hereinafter, a case where the ear hole opening
device 100 and the headphones 500 operate in cooperation with each other will be described
with reference to FIGS. 70 to 74.
(2) Second Combination Example
[0292] A second combination example is an example in which the headphones 500 perform the
noise cancellation process of the FB scheme based on an audio signal received from
the ear hole opening device 100. This example will be described with reference to
FIG. 70.
[0293] FIG. 70 is a diagram for describing the second combination example of the ear hole
opening device 100 and the headphones 500 according to the present embodiment. As
illustrated in FIG. 70, the ear hole opening device 100 and the headphones 500 are
worn in an overlapping manner. When worn in this manner, the wireless communication
unit 170 of the ear hole opening device 100 and the wireless communication unit 550
of the headphones 500 perform wireless communication. Then, the ear hole opening device
100 and the headphones 500 cooperate to perform the noise cancellation process. Specifically,
the audio signal generated by the microphone 141 is input to the wireless communication
unit 170 as illustrated in FIG. 70. Then, the wireless communication unit 170 wirelessly
transmits the audio signal generated by the microphone 141 to the headphones 500.
The wireless communication unit 550 receives the audio signal wirelessly transmitted
from the ear hole opening device 100. The wireless communication unit 550 outputs
the received audio signal to a FB filter 704. The FB filter 704 performs the noise
cancellation process of the FB scheme using the microphone 141 as a cancellation point
based on the input audio signal, and generates a noise cancellation signal. The generated
noise cancellation signal is input to an adder 703. The adder 703 synthesizes the
noise cancellation signal input from the FB filter 704 in addition to the noise cancellation
signals respectively input from the FB filter 701 and the FF filter 702, and outputs
the synthesized signal to the driver 110. The driver 110 outputs audio based on the
input synthesized signal.
[0294] Detailed signal processing is substantially the same as the first noise cancellation
process described above with reference to FIG. 32. That is, the FF filter 702 corresponds
to the FF filter 414, the FB filter 701 corresponds to the first FB filter 411, and
the FB filter 704 corresponds to the second FB filter 412. However, this example is
different from the first noise cancellation process described above with reference
to FIG. 32 in terms that the internal models illustrated in the blocks 441, 442, 443,
and 444 in FIG. 32 are not included.
[0295] Note that the noise cancellation process on the ear hole opening device 100 side
is not illustrated in FIG. 70, but it is a matter of course that the noise cancellation
process may also be performed on the ear hole opening device 100 side. For example,
the ear hole opening device 100 generates a noise cancellation signal based on the
audio signal generated by the microphone 141 and outputs the generated noise cancellation
signal from the driver 110. The same applies to the subsequent combination examples.
[0296] In addition, the case where the ear hole opening device 100 transmits the audio signal
generated by the microphone 141 to the headphones 500 has been described in the present
embodiment, but the present technique is not limited to such an example. For example,
another device may be interposed between the ear hole opening device 100 and the headphones
500. In addition, the headphones 500 may transmit the audio signal generated by the
FB-NC microphone 520-1 and/or the FF-NC microphone 520-2 to the ear hole opening device
100. The same applies to the subsequent combination examples.
(3) Third Combination Example
[0297] A third combination example is an example in which the headphones 500 perform the
noise cancellation process of the FB scheme in which an internal model is applied
based on an audio signal received from the ear hole opening device 100. This example
will be described with reference to FIG. 71.
[0298] FIG. 71 is a diagram for describing the third combination example of the ear hole
opening device 100 and the headphones 500 according to the present embodiment. Processing
blocks illustrated in FIG. 71 are obtained by adding an internal model 705 and an
adder 706 to the processing blocks illustrated in FIG. 70. An output signal output
from the adder 703 is input to the internal model 705. The internal model 705 has
a characteristic that simulates the characteristic from the input of the output signal
to the driver 510 to the generation of the audio signal by the microphone 141. The
audio signal that has passed through the internal model 705 is input to the adder
706. The adder 706 subtracts the signal that has passed through the internal model
705 from the audio signal generated by the microphone 141 to perform synthesis. Then,
the adder 706 outputs the synthesized signal to the FB filter 704.
[0299] Detailed signal processing is the same as the first noise cancellation process described
above with reference to FIG. 32. That is, the FF filter 702 corresponds to the FF
filter 414, the FB filter 701 corresponds to the first FB filter 411, and the FB filter
704 corresponds to the second FB filter 412. In addition, the internal model 705 corresponds
to the blocks 441, 442, 443, and 444, and the adder 706 corresponds to the adder 432.
(4) Fourth Combination Example
[0300] A fourth combination example is an example in which the headphones 500 perform the
noise cancellation process of the adaptive FF scheme based on an audio signal received
from the ear hole opening device 100. This example will be described with reference
to FIG. 72.
[0301] FIG. 72 is a diagram for describing the fourth combination example of the ear hole
opening device 100 and the headphones 500 according to the present embodiment. Processing
blocks illustrated in FIG. 72 are obtained by adding an adaptive control unit 707
instead of the FB filter 704 in the processing blocks illustrated in FIG. 70. An audio
signal generated based on audio collected by the FF-NC microphone 520-2 and the audio
signal received by the wireless communication unit 550 are input to the adaptive control
unit 707. The adaptive control unit 707 adaptively controls the characteristic of
the FF filter 702 based on these audio signals. Under the adaptive control by the
adaptive control unit 707, the FF filter 702 generates a noise cancellation signal
by the noise cancellation process of the FF scheme based on the input audio signals.
The noise cancellation signal generated by the FF filter 702 is synthesized with the
noise cancellation signal generated by the FB filter 701 by the adder 703. The synthesized
signal is output from the driver 510.
[0302] Detailed signal processing is the same as the second noise cancellation process described
above with reference to FIG. 33. That is, the FF filter 702 corresponds to the FF
filter 414, the FB filter 701 corresponds to the first FB filter 411, and the adaptive
control unit 707 corresponds to the adaptive control unit 415.
(5) Fifth Combination Example
[0303] A fifth combination example is a combination of the third combination example and
the fourth combination example. This example will be described with reference to FIG.
73.
[0304] FIG. 73 is a diagram for describing the fifth combination example of the ear hole
opening device 100 and the headphones 500 according to the present embodiment. Processing
blocks illustrated in FIG. 73 include the internal model 705 and the adder 706 illustrated
in FIG. 71 and the adaptive control unit 707 illustrated in FIG. 72.
[0305] Detailed signal processing is the same as the third noise cancellation process described
above with reference to FIG. 35. That is, the FF filter 702 corresponds to the FF
filter 414, the FB filter 701 corresponds to the first FB filter 411, the FB filter
704 corresponds to the second FB filter 412, and the adaptive control unit 707 corresponds
to the adaptive control unit 415. In addition, the internal model 705 corresponds
to the blocks 441, 442, 443, and 444, and the adder 706 corresponds to the adder 432.
(6) Sixth Combination Example
[0306] A sixth combination example is an example in which a noise cancellation signal is
output on the ear hole opening device 100 side in addition to the fifth combination
example. This example will be described with reference to FIG. 74.
[0307] FIG. 74 is a diagram for describing the sixth combination example of the ear hole
opening device 100 and the headphones 500 according to the present embodiment. Processing
blocks illustrated in FIG. 74 are obtained by adding the FB filter 601 to the processing
blocks illustrated in FIG. 73. The operation of the FB filter 601 is the same as described
above with reference to FIG. 66.
[0308] In this example, audio based on the noise cancellation signal is output from both
the driver 110 and the driver 310. If considering that the ear hole opening device
100 can be always worn by the user, it is assumed that a diaphragm of the driver 110
is smaller than the driver 310. Therefore, the ear hole opening device 100 generates
a noise cancellation signal for noise in a higher frequency range than a predetermined
frequency, and outputs audio based on the noise cancellation signal. On the other
hand, the headphones 500 generate a noise cancellation signal for noise in a lower
frequency range than the predetermined frequency, and output audio based on the noise
cancellation signal. For example, the ear hole opening device 100 targets a mid-high
range, and the headphones 500 target a low range. Note that the bands targeted by
both the ear hole opening device 100 and the headphones 500 may be duplicated. Due
to such sharing, power consumptions of both the ear hole opening device 100 and the
headphones 500 can be reduced.
[0309] Here, the audio output from the driver 110 is radiated in the vicinity of the ear
hole via the sound guide unit 120 in the ear hole opening device 100. Therefore, a
phase delay depending on the distance between the driver 110 and the microphone 141
can occur. Therefore, the ear hole opening device 100 may include, for example, a
balanced armature type second audio output unit at a position close to the holding
unit 130 in the sound guide unit 120. Then, the ear hole opening device 100 may output
audio based on the noise cancellation signal from the second audio output unit. In
this case, since the second audio output unit is closer to the microphone 141 than
the driver 110, the phase delay depending on the distance decreases. Further, the
second audio output unit is closer to the microphone 141 than the driver 310. Therefore,
it is desirable that the second audio output unit output the audio based on the noise
cancellation signal targeting the high range. As a result, the noise canceling performance
with respect to the high frequency noise can be improved.
<7. Summary>
[0310] Heretofore, each combination example has been described. According to each of these
combination examples, the same effect as the effect described in the second embodiment
is achieved. Further, according to the present embodiment, the user does not prepare
the headphones 300 having the ear canal microphone 320-3 described in the second embodiment
but wears the headphones 500 to overlap the ear hole opening device 100, whereby the
same effect can be easily obtained.
<3.4. Variations of Wireless Communication>
[0311] The ear hole opening device 100 and the headphones 500 can perform wireless communication
by an arbitrary scheme. Here, as an example, wireless communication processing using
optical communication will be described with reference to FIGS. 75 to 77. Thereafter,
wireless communication processing using NFMI will be described with reference to FIG.
78. Note that it is assumed in the following description that the ear hole opening
device 100 and the headphones 500 have active batteries and circuits, respectively.
In addition, a description will be given on the assumption that wireless transmission
is performed from the ear hole opening device 100 to the headphones 500.
(1) Case of Communication Using Light
[0312] FIG. 75 is a diagram for describing an example of wireless communication processing
using light between the ear hole opening device 100 and the headphones 500 according
to the present embodiment. In particular, FIG. 75 illustrates processing blocks for
transmission in an analog system. First, processing of the ear hole opening device
100, which is a transmission side, will be described. An audio signal (analog signal)
generated by the microphone 141 is input to an amplifier 613 via a capacitor 611 and
a resistor 612. The audio signal is amplified by the amplifier 613 and radiated as
light from an optical transmission unit 615 via a resistor 614. Next, processing of
the headphones 500, which is a reception side, will be described. An optical reception
unit 711 receives the light emitted from the optical transmission unit 615 and outputs
a signal indicating the reception result. The signal indicating the reception result
is input to a resistor 712. A voltage at the microphone 141 and a voltage generated
at the resistor 712 have a proportional relationship. Therefore, the headphones 500
acquire the audio signal generated by the microphone 141 based on the voltage at the
resistor 712.
[0313] FIG. 76 is a diagram for describing an example of wireless communication processing
using light between the ear hole opening device 100 and the headphones 500 according
to the present embodiment. In particular, FIG. 76 illustrates processing blocks for
transmission in a digital system. First, processing of the ear hole opening device
100, which is a transmission side, will be described. An audio signal (analog signal)
generated by the microphone 141 is input to an ADC 621 via the capacitor 611. The
audio signal is converted to a digital signal by the ADC 621, modulated by a digital
modulation unit 622, and then converted to an analog signal by a DAC 623. Thereafter,
the audio signal is emitted as light from the optical transmission unit 615 via the
capacitor 624, the amplifier 613, and the resistor 614. Next, processing of the headphones
500, which is a reception side, will be described. An optical reception unit 711 receives
the light emitted from the optical transmission unit 615 and outputs a signal indicating
the reception result. A signal indicating the reception result is input to the ADC
722 via a capacitor 721 parallel to the resistor 712. The ADC 722 converts the input
signal into a digital signal and outputs the digital signal to a digital demodulation
unit 723. The digital demodulation unit 723 demodulates the input signal. In this
manner, the headphones 500 acquire the audio signal generated by the microphone 141
as the digital signal.
[0314] FIG. 77 is a diagram for describing an example of wireless communication processing
using light between the ear hole opening device 100 and the headphones 500 according
to the present embodiment. In particular, processing blocks using delta-sigma modulation
are illustrated in FIG. 77. First, processing of the ear hole opening device 100,
which is a transmission side, will be described. An audio signal (analog signal) generated
by the microphone 141 is input to a delta-sigma modulation unit 631 via the capacitor
611, and delta-sigma modulation is applied. The delta-sigma modulation unit 631 converts
the audio signal, which is originally the analog signal, into a 1-bit signal and outputs
the converted signal. The signal output from the delta-sigma modulation unit 631 is
radiated as light from the optical transmission unit 615 via the capacitor 632, the
amplifier 613, and the resistor 614. Next, processing of the headphones 500, which
is a reception side, will be described. An optical reception unit 711 receives the
light emitted from the optical transmission unit 615 and outputs a signal indicating
the reception result. The signal indicating the reception result passes through a
capacitor 731 parallel to the resistor 712, is demodulated into a digital signal by
the digital modulation unit 732, and is down-sampled by a down-sampling unit 733.
In this manner, the headphones 500 acquire the audio signal generated by the microphone
141 as the digital signal. Since the delta-sigma modulation is used according to the
wireless communication processing illustrated in FIG. 77, a calculation time required
for modulation is little, and high-speed transmission at several MHz/bit is possible
as compared with the wireless communication processing illustrated in FIG. 76. For
this reason, the headphones 500 can receive the audio signal generated by the microphone
141 with an ultra-low delay and can use the received audio signal for the noise cancellation
process.
(2) Case of Communication Using NFMI
[0315] FIG. 78 is a diagram for describing an example of wireless communication processing
using NFMI between the ear hole opening device 100 and headphones 500 according to
the present embodiment. First, processing of the ear hole opening device 100, which
is a transmission side, will be described. As illustrated in FIG. 78, the ear hole
opening device 100 includes a resistor 641, a capacitor 642, and an inductor 643.
An audio signal (analog signal) generated by the microphone 141 is input to the capacitor
642 and the inductor 643 after passing through the resistor 641. The inductor 643
generates magnetism corresponding to the input signal. Next, processing of the headphones
500, which is a reception side, will be described. As illustrated in FIG. 78, the
headphones 500 include a resistor 741, a capacitor 742, and an inductor 743. The inductor
743 resonates with the magnetism generated by the inductor 643 and generates and outputs
a signal similar to the signal that has been input to the inductor 643. In this manner,
the headphones 500 acquire the audio signal generated by the microphone 141.
<3.5. Mutual Device Detection>
[0316] A user wears the headphones 500 in an overlapping manner in the state of wearing
the ear hole opening device 100. What is considered as the motive thereof is that
the user desires a stronger noise canceling effect than that in the case of using
the ear hole opening device 100 alone.
[0317] Therefore, it is desirable that the noise cancellation process according to any of
the first to sixth combination examples described above be started when detecting
that the headphones 500 are worn outside the ear hole opening device 100. Therefore,
the ear hole opening device 100 and the headphones 500 detect mutual devices in the
case of being worn in the overlapping manner, and start the noise cancellation process.
For example, if any one power is off, the power is turned on. In addition, wireless
communication is started if the wireless communication has not been performed. That
is, the ear hole opening device 100 starts transmitting the audio signal generated
by the microphone 141 to the headphones 500, and the headphones 500 start receiving
the audio signal from the ear hole opening device 100. As a result, the user can automatically
enjoy the strong noise canceling effect simply by wearing the headphones 500 to overlap
the ear hole opening device 100. Hereinafter, this point will be described in detail.
(1) Contactless Power Supply
[0318] The wearing of the headphones 500 on the outer side of the ear hole opening device
100 may be detected based on contactless power supply performed between the ear hole
opening device 100 and the headphones 500. The contactless power supply may be performed
from the headphones 500 to the ear hole opening device 100, or may be performed from
the ear hole opening device 100 to the headphones 500. Hereinafter, these two systems
will be described.
• Contactless Power Supply from Headphones 500 to Ear Hole Opening Device 100
[0319] The power of the ear hole opening device 100 may be turned on when contactless power
supply is performed from the headphones 500 in the power-off state. For example, when
the contactless power supply is performed from the headphones 500, the operation control
unit 153 is first activated. Next, the operation control unit 153 turns on the power
of the ear hole opening device 100 using the battery power provided in the ear hole
opening device 100. Thereafter, the operation control unit 153 causes the wireless
communication unit 170 to start wireless communication. The wireless communication
unit 170 starts transmitting the audio signal generated by the microphone 141 to the
headphones 500.
[0320] The headphones 500 include a contactless power supply unit that performs contactless
power supply to the ear hole opening device 100. The contactless power supply unit
attempts contactless power supply to the ear hole opening device 100. The contactless
power supply unit may attempt the contactless power supply with detection of wearing
of the ear hole opening device 100 and the headphones 500 in an overlapping manner
as a trigger, or may periodically attempt the contactless power supply without the
trigger. When the contactless power supply unit has performed the contactless power
supply to the ear hole opening device 100 (that is, when the contactless power supply
has succeeded), the wireless communication unit 550 starts receiving the audio signal
generated by the microphone 141 from the ear hole opening device 100.
• Contactless Power Supply from Ear Hole Opening Device 100 to Headphones 500
[0321] The power of the headphones 500 may be turned on when contactless power supply is
performed from the ear hole opening device 100 in the power-off state. For example,
when the contactless power supply is performed from the ear hole opening device 100,
the operation control unit 533 is first activated. Next, the operation control unit
533 turns on the power of the headphones 500 using the battery power provided in the
headphones 500. Thereafter, the operation control unit 533 causes the sensor unit
540 to start wireless communication. For example, the wireless communication unit
550 starts receiving the audio signal generated by the microphone 141.
[0322] The ear hole opening device 100 includes a contactless power supply unit that performs
contactless power supply to the headphones 500. The contactless power supply unit
attempts contactless power supply to the headphones 500. The contactless power supply
unit may attempt the contactless power supply with detection of wearing of the ear
hole opening device 100 and the headphones 500 in an overlapping manner as a trigger,
or may periodically attempt the contactless power supply without the trigger. When
the contactless power supply unit has performed the contactless power supply to the
headphones 500 (that is, when the contactless power supply has succeeded), the wireless
communication unit 170 starts transmitting the audio signal generated by the microphone
141 to the headphones 500.
• Example of Contactless Power Supply Using RFID Device
[0323] The contactless power supply described above can be performed by an RFID device.
When a reader reads an RF tag, the RF tag is energized by a radio wave emitted from
the reader. As a result, the side having the RF tag detects a device having the reader.
Meanwhile, tag data stored in the RF tag is returned from the RF tag to the reader
side with the energization of the RF tag as a trigger. As a result, the side having
the reader detects a device having the RF tag. For the contactless power supply, an
arbitrary scheme, such as an electromagnetic induction scheme and a magnetic field
resonance scheme, can be adopted in addition to a radio wave reception scheme such
as the RFID device. Hereinafter, a configuration in which the ear hole opening device
100 and the headphones 500 include the RFID device will be described with reference
to FIG. 79.
[0324] FIG. 79 is a view for describing mutual device detection using the RFID device performed
by the ear hole opening device 100 and the headphones 500 according to the present
embodiment. As illustrated in FIG. 79, the headphones 500 are provided with an RFID
device 541 on a side wall 502b at the inner side of the contact surface 502a of the
ear pad. In addition, the ear hole opening device 100 is provided with an RFID device
161 near the holding unit 130 of the sound guide unit 120. The contactless power supply
from the headphones 500 to the ear hole opening device 100 is realized when the RFID
device 541 is a reader and the RFID device 161 is an RF tag. On the other hand, the
contactless power supply from the ear hole opening device 100 to the headphones 500
is realized when the RFID device 161 is a reader and the RFID device 541 is an RF
tag. Each of the RFID device 541 and the RFID device 161 may include both the reader
and the RF tag. When the ear hole opening device 100 and the headphones 500 are worn
in an overlapping manner, the RFID device 541 and the RFID device 161 are close to
each other. As a result, energization and reading are performed between the RF tag
and the RF reader, and the mutual device detection is performed.
[0325] Hereinafter, an example of processing process when a noise cancellation process is
started based on the contactless power supply from the headphones 500 to the ear hole
opening device 100 will be described with reference to FIG. 80.
[0326] FIG. 80 is a sequence diagram illustrating an example of the processing flow when
the noise cancellation process according to the present embodiment is started based
on the contactless power supply from the headphones 500 to the ear hole opening device
100. As illustrated in FIG. 80, the ear hole opening device 100 and the headphones
500 are involved in this sequence. This sequence is a sequence when the ear hole opening
device 100 has an RF tag and the headphones 500 have a reader.
[0327] It is assumed that the headphones 500 are in the power-on state at the start time
(Step S202), and the ear hole opening device 100 is in either the power-off state
or the power-on state (Step S302). The headphones 500 start reading the RF tag by
the reader (Step S204). Power is supplied to the RF tag from the reader, and the RF
tag of the ear hole opening device 100 is energized (Step S304), and tag data is returned
from the RF tag to the reader side (Step S306).
[0328] The power of the ear hole opening device 100 is turned on in the power-off state
with the energization of the RF tag as a trigger (Step S308). Thereafter, the ear
hole opening device 100 is wirelessly connected to the headphones 500 (Step S310).
Then, the ear hole opening device 100 transmits microphone data (that is, the audio
signal generated by the microphone 141) to the headphones 500 (Step S312). Thereafter,
the ear hole opening device 100 performs a prescribed operation relating to the noise
cancellation process described above.
[0329] The headphones 500 determine whether the tag data from the RF tag has been read (Step
S206). When it is determined that the tag data from the RF tag is not readable (Step
S206/NO), the headphones 500 increment a reading failure count (Step S208). Next,
the headphones 500 determine whether the reading failure count has reached a predetermined
number (Step S210). When it is determined that the reading failure count has reached
the predetermined number (Step S210/YES), the processing ends. On the other hand,
when it is determined that the reading failure count has not reached the predetermined
number (Step S210/NO), the processing returns to Step S204 again. In addition, when
it is determined that the tag data from the RF tag has been read (Step S206/YES),
the headphones 500 are wirelessly connected to the ear hole opening device 100 (Step
S212). Then, the headphones 500 receive the microphone data from the ear hole opening
device 100 (Step S312). Thereafter, the headphones 500 perform a prescribed operation
relating to the noise cancellation process described above.
[0330] Next, an example of processing flow when the noise cancellation process is started
based on the contactless power supply from the ear hole opening device 100 to the
headphones 500 will be described with reference to FIG. 81.
[0331] FIG. 81 is a sequence diagram illustrating an example of the processing flow when
the noise cancellation process according to the present embodiment is started based
on the contactless power supply from the ear hole opening device 100 to the headphones
500. As illustrated in FIG. 81, the ear hole opening device 100 and the headphones
500 are involved in this sequence. In this sequence, the ear hole opening device 100
has a reader, and the headphones 500 have an RF tag.
[0332] It is assumed that the headphones 500 are in the power-off state at the start time
(Step S222), and the ear hole opening device 100 is in the power-on state (Step S322).
The ear hole opening device 100 starts reading the RF tag by the reader (Step S324).
Power is supplied to the RF tag from the reader, and the RF tag of the headphones
500 is energized (Step S224), and tag data is returned from the RF tag to the reader
side (Step S226).
[0333] The ear hole opening device 100 determines whether the tag data from the RF tag has
been read (Step S326). When it is determined that the tag data from the RF tag is
not readable (Step S326/NO), the ear hole opening device 100 increments a reading
failure count (Step S328). Next, the ear hole opening device 100 determines whether
the reading failure count has reached a predetermined number (Step S330). When it
is determined that the reading failure count has reached the predetermined number
(Step S330/YES), the processing ends. On the other hand, when it is determined that
the reading failure count has not reached the predetermined number (Step S330/NO),
the processing returns to Step S324 again. In addition, when it is determined that
the tag data from the RF tag has been read (Step S326/YES), the ear hole opening device
100 is wirelessly connected to the headphones 500 (Step S332), and microphone data
(that is, the audio signal generated by the microphone 141) is transmitted to the
headphones 500 (Step S334). Thereafter, the ear hole opening device 100 performs a
prescribed operation relating to the noise cancellation process described above.
[0334] The power of the headphones 500 is turned on with the energization of the RF tag
as a trigger (Step S228). Thereafter, the headphones 500 are wirelessly connected
to the ear hole opening device 100 (Step S230). Then, the headphones 500 receive the
microphone data (that is, the audio signal generated by the microphone 141) from the
ear hole opening device 100 (Step S334). Thereafter, the headphones 500 perform a
prescribed operation relating to the noise cancellation process described above.
(2) NFMI
[0335] The wearing of the headphones 500 on the outer side of the ear hole opening device
100 may be detected based on magnetic resonance performed between the ear hole opening
device 100 and the headphones 500. When the ear hole opening devices 100 are worn
on both left and right ears, the left and right ear hole opening devices 100 can transmit
and receive a music signal and the like by NFMI. When the headphones 500 are worn
to overlap the left and right ear hole opening devices 100, the headphones 500 may
detect the communication between the left and right ear hole opening devices 100 by
the NFMI and start the noise cancellation process. Hereinafter, this point will be
described with reference to FIGS. 82 to 85.
[0336] FIGS. 82 to 85 are views for describing mutual device detection using NFMI performed
by the ear hole opening devices 100 and the headphones 500 according to the present
embodiment. In FIGS. 82 to 85, "A" is added to each end of reference signs of constituent
elements of an ear hole opening device 100A, and "B" is added to each end of reference
signs of constituent element of an ear hole opening device 100B. In addition, among
constituent elements of the headphones 500, "A" is added to each end of reference
signs of constituent element adjacent to the ear hole opening device 100A, and "B"
is added to each end of reference signs of constituent element adjacent to the ear
hole opening device 100B. The terminal device 800 is an arbitrary device such as a
tablet terminal, a smartphone, and an agent device.
[0337] As illustrated in FIG. 82, it is assumed that a user wears the ear hole opening device
100A in one ear and the ear hole opening device 100B in the other ear. The terminal
device 800 transmits a music signal using an arbitrary communication scheme such as
Bluetooth or Wi-Fi. A wireless communication unit 170A receives the music signal transmitted
by the terminal device 800, and a driver 110A outputs music based on the received
music signal. In addition, the wireless communication unit 170A transfers the music
signal to the ear hole opening device 100B using NFMI. A wireless communication unit
170B receives the transferred music signal, and a driver 110B outputs music based
on the received music signal.
[0338] Next, it is assumed that the user wears the headphones 500 to overlap the ear hole
opening devices 100A and 100B as illustrated in FIG. 83. In this case, NFMI transceivers
of wireless communication units 550A and 550B of the headphones 500 also resonate
with the music signal transmitted from the ear hole opening device 100A to the ear
hole opening device 100B using NFMI. The headphones 500 detect that the headphones
500 have been worn to overlap the ear hole opening devices 100A and 100B by such magnetic
resonance. Similarly, the ear hole opening devices 100A and 100B also detect that
the headphones 500 have been worn in the overlapping manner.
[0339] Thereafter, the headphones 500 and the ear hole opening devices 100A and 100B start
a noise cancellation process as illustrated in FIG. 84. Specifically, the ear hole
opening device 100A transmits microphone data generated by a microphone 141A by the
wireless communication unit 170A. For example, the wireless communication unit 170A
stops transferring the music signal using NFMI and transmits microphone data using
NFMI. The microphone data transmitted from the wireless communication unit 170A is
received by the wireless communication unit 550A adjacent to the wireless communication
unit 170A. The headphones 500 perform the noise cancellation process based on the
received audio signal, and output a generated noise cancellation signal from a driver
510A. The same applies to the ear hole opening device 100B.
[0340] As illustrated in FIG. 85, the headphones 500 may perform reception of a music signal
and distribution of the music signal to the right and left. Specifically, first, the
wireless communication unit 550A receives a music signal transmitted from the terminal
device 800. The wireless communication unit 550A outputs the music signal received
from terminal device 800 and microphone data received from the ear hole opening device
100A to the signal processing unit 531. In addition, the wireless communication unit
550B outputs the microphone data received from the ear hole opening device 100B to
the signal processing unit 531. The signal processing unit 531 generates a noise cancellation
signal based on the microphone data received from the ear hole opening devices 100A
and 100B, and generates a synthesized signal by synthesizing the music signal with
the generated noise cancellation signal. The synthesized signal is input to the driver
510A and a driver 510B, and is output as audio. With such processing, it is possible
to realize seamless transition mainly for music reproduction without causing the user
to feel uncomfortable due to interruption of the music reproduction before and after
wearing the headphones 500.
[0341] Since NFMI does not particularly require pairing or the like, the above mutual device
detection is possible. Of course, only paired devices may be subjected to the mutual
device detection.
[0342] Hereinafter, an example of processing flow when the noise cancellation process is
started based on the magnetic resonance among the ear hole opening devices 100 and
the headphones 500 will be described with reference to FIG. 86.
[0343] FIG. 86 is a sequence diagram illustrating an example of the processing flow when
the noise cancellation process according to the present embodiment is started based
on the magnetic resonance among the ear hole opening devices 100 and the headphones
500. As illustrated in FIG. 86, the ear hole opening device 100 and the headphones
500 are involved in this sequence.
[0344] At the start time, the headphones 500 are in the power-on state (Step S242). In addition,
the ear hole opening device 100 is in the power-on state (Step S342), and performs
NFMI communication with the other ear hole opening device 100 (Step S344).
[0345] The ear hole opening device 100 determines whether a prescribed signal transmitted
by NFMI has been detected during the NFMI communication (Step S346). When it is determined
that the prescribed signal transmitted by NFMI has not been detected (Step S346/NO),
the processing returns to Step S346 again. On the other hand, when it is determined
that the prescribed signal transmitted by NFMI has been detected (Step S346/YES),
the ear hole opening device 100 changes an operation mode from an operation mode of
performing NFMI communication with the other ear hole opening device 100 to an operation
mode of performing NFMI communication with the headphones 500, and is wirelessly connected
to the headphones 500 by NFMI (Step S348). Then, the ear hole opening device 100 transmits
microphone data (that is, the audio signal generated by the microphone 141) to the
headphones 500 (Step S350). Thereafter, the ear hole opening device 100 performs a
prescribed operation relating to the noise cancellation process described above.
[0346] The headphones 500 start detecting NFMI communication (Step S244), and determine
whether the NFMI communication has been detected (Step S246). When it is determined
that the NFMI communication has not been detected (Step S246/NO), the headphones 500
increment a reading failure count (Step S248). Next, the headphones 500 determine
whether the reading failure count has reached a predetermined number (Step S250).
When it is determined that the reading failure count has reached the predetermined
number (Step S250/YES), the processing ends. On the other hand, when it is determined
that the reading failure count has not reached the predetermined number (Step S250/NO),
the processing returns to Step S244 again. When it is determined that the FMI communication
has been detected (Step S246/YES), the headphones 500 transmits the prescribed signal
by NFMI (Step S252). Then, the headphones 500 are wirelessly connected to the ear
hole opening device 100 by NFMI (Step S254), and receives the microphone data from
the ear hole opening device 100 (Step S350). Thereafter, the headphones 500 perform
a prescribed operation relating to the noise cancellation process described above.
(3) Audio
[0347] The wearing of the headphones 500 on the outer side of the ear hole opening device
100 may be detected based on collection of predetermined audio by the ear hole opening
devices 100 or the headphones 500. This point will be described with reference to
FIG. 87.
[0348] FIG. 87 is a diagram for describing mutual device detection using audio by the ear
hole opening device 100 and the headphones 500 according to the present embodiment.
For example, the headphones 500 output predetermined audio when it is detected that
the headphones 500 are worn by a user. The wearing/non-wearing by the user can be
detected based on the deformation of the ear pad 502 detected by, for example, a pressure-sensitive
sensor. When the predetermined audio is collected by the microphone 141, the ear hole
opening device 100 detects that the headphones 500 are worn in an overlapping manner.
The predetermined audio may be audio in an ultrasonic region above the audible band.
In this case, the mutual device detection can be performed without causing discomfort
to the user. In addition, the ear hole opening device 100 may output predetermined
audio and the headphones 500 may collect the audio conversely to the example illustrated
in FIG. 87.
(4) Magnetism of Driver
[0349] The wearing of the headphones 500 on the outer side of the ear hole opening device
100 may be detected based on detection of predetermined magnetism by the ear hole
opening devices 100 or the headphones 500. This point will be described with reference
to FIG. 88.
[0350] FIG. 88 is a diagram for describing mutual device detection using magnetism by the
ear hole opening device 100 and the headphones 500 according to the present embodiment.
For example, the ear hole opening device 100 is provided with a magnetic sensor 162
near the holding unit 130 of the sound guide unit 120. The driver 510 of the headphones
500 includes a magnet and emits magnetism 751. Therefore, the ear hole opening device
100 detects that the headphones 500 are worn in an overlapping manner based on the
detection of the magnetism 751 by the magnetic sensor 162. The headphones 500 may
be provided with a magnetic sensor to detect magnetism from the driver 110 of the
ear hole opening device 100 conversely to the example illustrated in FIG. 88.
<3.6. Summary>
[0351] The third embodiment has been described in detail above. As described above, the
ear hole opening device 100 and the headphones 500 that are worn by the user in the
overlapping manner can cooperate with each other by wireless communication according
to the third embodiment. Specifically, the ear hole opening device 100 transmits the
audio signal generated by the audio input unit 141 to the headphones 500. The headphones
500 perform the noise cancellation process based on the received audio signal. Since
the headphones 500 can perform the noise cancellation process based on the sound collection
result at the position close to the eardrum, high noise canceling performance can
be realized.
<<4. Hardware Configuration Example>>
[0352] Finally, a hardware configuration of an information processing apparatus according
to each embodiment will be described with reference to FIG. 89. FIG. 89 is a block
diagram illustrating an example of the hardware configuration of the information processing
apparatus according to each embodiment. Note that an information processing apparatus
900 illustrated in FIG. 89 can realize, for example, the ear hole opening device 100
illustrated in FIG. 3, the headphones 300 illustrated in FIG. 31, the ear hole opening
device 100 illustrated in FIG. 65, and the headphones 500 illustrated in FIG. 67.
Information processing performed by the ear hole opening device 100, the headphones
300, or the headphones 500 according to the present embodiment is realized by cooperation
between software and hardware to be described hereinafter.
[0353] As illustrated in FIG. 89, the information processing apparatus 900 includes a central
processing unit (CPU) 901, a read-only memory (ROM) 902, a random-access memory (RAM)
903, and a host bus 904a. In addition, the information processing apparatus 900 includes
a bridge 904, an external bus 904b, an interface 905, an input device 906, an output
device 907, a storage device 908, a drive 909, a connection port 911, and a communication
device 913. The information processing apparatus 900 may include an electric circuit
and a processing circuit such as a DSP and an ASIC instead of or in addition to the
CPU 901.
[0354] The CPU 901 functions as an arithmetic processing device and a control device, and
controls the overall operations in the information processing apparatus 900 according
to various programs. In addition, the CPU 901 may be a microprocessor. The ROM 902
stores programs to be used by the CPU 901, calculation parameters, and the like. The
RAM 903 temporarily stores programs used in the execution of the CPU 901, parameters
and the like that appropriately change during the execution. The CPU 901 can form,
for example, the control unit 150 illustrated in FIG. 3, the control unit 330 illustrated
in FIG. 31, the control unit 150 illustrated in FIG. 65, or the control unit 530 illustrated
in FIG. 67.
[0355] The CPU 901, the ROM 902, and the RAM 903 are mutually connected by the host bus
904a including a CPU bus and the like. The host bus 904a is connected to the external
bus 904b such as a peripheral component interconnect/interface (PCI) bus via the bridge
904. The host bus 904a, the bridge 904, and the external bus 904b are not necessarily
configured to be separate from each other, and these functions may be implemented
on one bus.
[0356] The input device 906 is realized by a device that can collect audio and generate
an audio signal, for example, a microphone, an array microphone, or the like. In addition,
the input device 906 includes a distance measurement sensor and a circuit that processes
vibration information obtained by the distance measurement sensor, and is realized
by a device that can acquire sound pressure information at a distant position. These
input devices 906 can form, for example, the audio information acquisition unit 140
illustrated in FIG. 3, the audio input unit 320 illustrated in FIG. 31, the audio
information acquisition unit 140 illustrated in FIG. 65, or the audio input unit 520
illustrated in FIG. 67.
[0357] In addition, the input device 906 can be formed using a device that detects various
types of information. For example, the input device 906 can include various sensors
such as an image sensor (for example, a camera), a depth sensor (for example, a stereo
camera), an acceleration sensor, a gyro sensor, a magnetic sensor, a geomagnetic sensor,
an optical sensor, a sound sensor, a distance sensor, and a force sensor. In addition,
the input device 906 may acquire information on the information processing device
900 itself, such as an attitude and a movement speed of the information processing
device 900 and information on the surrounding environment of the information processing
apparatus 900 such as brightness and noise around the information processing device
900. In addition, the input device 906 may include a global navigation satellite system
(GNSS) module that receives a GNSS signal from a GNSS satellite (for example, a global
positioning system (GPS) signal from a GPS satellite) to measure position information
including latitude, longitude, and altitude of a device. In addition, regarding the
position information, the input device 906 may detect a position by transmission/reception
with Wi-Fi (registered trademark), a mobile phone/PHS/smartphone, and the like or
near field communication. These input devices 906 can form, for example, the sensor
unit 370 illustrated in FIG. 31, the sensor unit 160 illustrated in FIG. 65, or the
sensor unit 540 illustrated in FIG. 67.
[0358] The output device 907 is an audio output device that can output audio such as a speaker,
a directional speaker, and a bone conduction speaker. The output device 907 can form,
for example, the audio output unit 110 illustrated in FIG. 3, the audio output unit
310 illustrated in FIG. 31, the audio output unit 110 illustrated in FIG. 65, or the
audio output unit 510 illustrated in FIG. 67.
[0359] The storage device 908 is a device for data storage which is formed as an example
of a storage unit of the information processing apparatus 900. The storage device
908 is realized by, for example, a magnetic storage unit device such as an HDD, a
semiconductor storage device, an optical storage device, a magneto-optical storage
device, or the like. The storage device 908 may include a storage medium, a recording
device that records data in the storage medium, a reading device that reads data from
the storage medium, a deletion device that deletes data recorded in the storage medium,
and the like. The storage device 908 stores programs to be executed by the CPU 901,
various types of data, various types of data acquired from the outside, and the like.
[0360] The drive 909 is a reader/writer for a storage medium, and is built in or externally
attached to the information processing apparatus 900. The drive 909 reads information
recorded in an attached removable storage medium, such as a magnetic disk, an optical
disk, a magneto-optical disk, or a semiconductor memory, and outputs the read information
to the RAM 903. In addition, the drive 909 can also write information to the removable
storage medium.
[0361] The connection port 911 is an interface to be connected to an external device, and
is a connection port with the external device capable of data transmission, for example,
by universal serial bus (USB) or the like.
[0362] The communication device 913 is, for example, a communication interface formed using
a communication device or the like for connection to a network 920. The communication
device 913 is, for example, a communication card or the like for wired or wireless
local area network (LAN), long term evolution (LTE), Bluetooth (registered trademark),
or wireless USB (WUSB). In addition, the communication device 913 may be a router
for optical communication, a router for asymmetric digital subscriber line (ADSL),
a modem for various communications, or the like. The communication device 913 can
transmit and receive a signal and the like according to a predetermined protocol,
for example, TCP/IP or the like with the Internet or another communication device.
The communication device 913 can form, for example, the wireless communication unit
170 illustrated in FIG. 65 or the wireless communication unit 550 illustrated in FIG.
67.
[0363] The network 920 is a wired or wireless transmission path of information to be transmitted
from a device connected to the network 920. For example, the network 920 may include
a public line network such as the Internet, a telephone line network, and a satellite
communication network, various local area networks (LAN) including Ethernet (registered
trademark), a wide area network (WAN), and the like. In addition, the network 920
may include a dedicated line network such as an Internet protocol-virtual private
network (IP-VPN).
[0364] The example of the hardware configuration capable of realizing the functions of the
information processing apparatus 900 according to the present embodiment has been
illustrated above. Each of the constituent elements described above may be realized
using a general-purpose member, or may be realized by hardware dedicated for the function
of each constituent element. Therefore, it is possible to change the hardware configuration
to be used as appropriate according to a technical level at the time of implementing
the present embodiment.
[0365] Note that a computer program configured to realize each function of the information
processing apparatus 900 according to the present embodiment as described above can
be created and mounted on a PC or the like. In addition, a computer-readable recording
medium in which such a computer program is stored can be provided. The recording medium
is, for example, a magnetic disk, an optical disk, a magneto-optical disk, a flash
memory, or the like. In addition, the above computer program may be distributed via,
for example, a network without using the recording medium.
<<5. Summary>>
[0366] The embodiments of the present disclosure have been described above with reference
to FIGS. 1 to 89.
[0367] The ear hole opening device 100 according to the first embodiment opens the ear hole
to the outside through the opening portion 131 while holding the audio information
acquisition unit 140 acquiring the audio information in the space closer to the eardrum
than the tragus using the holding unit 130 that abuts on the cavum concha or the inner
wall of the ear canal. Then, the ear hole opening device 100 generates the noise cancellation
signal based on the audio information acquired by the audio information acquisition
unit 140. For example, the ear hole opening device 100 performs the noise cancellation
process using the position of the audio information acquisition unit 140 or the eardrum
position as the cancellation point. Since the position near the eardrum or the eardrum
is the cancellation point, the high noise canceling performance can be realized.
[0368] The headphones 300 according to the second embodiment include the three microphones
320-1 to 320-3 that are arranged on one ear side of the user in the state of being
worn by the user. Then, the headphones 300 perform the noise cancellation processes
to generate the plurality of noise cancellation signals based on the three audio signals
generated by the three microphones 320-1 to 320-3. Although the maximum number of
microphones is two in the typical headphones equipped with the noise cancellation
function, the headphones 300 have the three microphones. In particular, the ear canal
microphone 320-3 is arranged near the entrance of the ear canal in the worn state.
Therefore, the headphones 300 can perform the noise cancellation process based on
appropriate information such as the audio signals generated by many microphones or
the audio signal generated by microphone arranged near the entrance of the ear canal.
[0369] In addition, the headphones 300 according to the second embodiment include the housing
301, the ear pad 302, the ear canal microphone 320-3, and the driver 310. Then, the
headphones 300 open the ear hole to the inner space of the headphones 300 through
the opening portion 304 while holding the ear canal microphone 320-3 in the space
closer to the eardrum side than the tragus by the holding unit 130 that abuts on the
cavum concha or the inner wall of the ear canal in the worn state. With such a configuration,
the ear canal microphone 320-3 is held in the space closer to the eardrum side than
the tragus. Therefore, the headphones 300 can set the cancellation point of the noise
cancellation process to be closer to the user's eardrum than the typical headphones
having the combination-type noise cancellation function.
[0370] The ear hole opening device 100 according to the third embodiment wirelessly communicates
with headphones 500 that are worn to overlap the outer side of the ear hole opening
device 100 worn by the user. Similarly, the headphones 300 according to the third
embodiment wirelessly communicate with the ear hole opening device 100 worn to overlap
the inner side of the headphones 500 worn by the user. In this manner, the ear hole
opening device 100 and the headphones 500, which are worn in the overlapping manner,
can cooperate by wireless communication. Specifically, the ear hole opening device
100 transmits the audio signal generated by the audio input unit 141 to the headphones
500. The headphones 500 perform the noise cancellation process based on the received
audio signal. Since the headphones 500 can perform the noise cancellation process
based on the sound collection result at the position close to the eardrum, high noise
canceling performance can be realized.
[0371] Although the preferred embodiments of the present disclosure have been described
as above in detail with reference to the accompanying drawings, a technical scope
of the present disclosure is not limited to such examples. It is apparent that a person
who has ordinary knowledge in the technical field of the present disclosure can find
various alterations and modifications within the scope of technical ideas described
in the claims, and it should be understood that such alterations and modifications
will naturally pertain to the technical scope of the present disclosure.
[0372] In addition, the processing described with reference to the flowcharts and sequence
diagrams in the present specification are not necessarily executed in the illustrated
order. Some processing steps may be executed in parallel. In addition, additional
processing steps may be adopted, and some processing steps may be omitted.
[0373] In addition, the effects described in the present specification are merely illustrative
or exemplary, and are not limited. That is, the technique according to the present
disclosure can exhibit other effects apparent to those skilled in the art on the basis
of the description of the present specification, in addition to or instead of the
above-described effects.
[0374] Note that the following configurations also belong to the technical scope of the
present disclosure.
- (1) A headphone device comprising:
a housing;
an audio input unit that is arranged to be separated from the housing and collects
audio to generate an audio signal;
a holding unit that abuts on a cavum concha or an inner wall of an ear canal of a
user and holds the audio input unit in a space closer to an eardrum side than a tragus,
in a state of being worn by the user;
a wired connection unit that connects the housing and the audio input unit in a wired
manner;
a signal processing unit that generates a noise cancellation signal for an external
sound based on the audio signal generated by the audio input unit, and generates an
output signal based on the generated noise cancellation signal; and
an audio output unit that outputs audio based on the output signal.
- (2) The headphone device according to (1), wherein the holding unit holds the audio
input unit in a space up to 15 mm away from a boundary between the cavum concha and
the ear canal to the eardrum side or in a space up to 15 mm away from the boundary
between the cavum concha and the ear canal on an opposite side of the eardrum.
- (3) The headphone device according to (1) or (2), wherein the holding unit further
comprises an opening portion that opens an ear hole to a space formed by the housing,
an ear pad, and a head of the user.
- (4) The headphone device according to any one of (1) to (3), wherein the housing comprises
a winding unit that winds up the wired connection unit.
- (5) The headphone device according to any one of (1) to (4), wherein the housing comprises
a recess capable of accommodating the holding unit and the audio input unit on a space
side formed by the housing, an ear pad, and a head of the user.
- (6) The headphone device according to (5), wherein the signal processing unit starts
or stops generating the noise cancellation signal based on whether the holding unit
and the audio input unit are accommodated in the recess.
- (7) The headphone device according to any one of (1) to (6), further comprising a
support member having one end connected to the housing and another end connected to
the holding unit.
- (8) The headphone device according to (7), wherein the wired connection unit is stored
inside the support member.
- (9) The headphone device according to (7) or (8), further comprising
a plurality of the support members,
wherein the one ends of the plurality of support members are connected to the housing
at positions different from each other.
- (10) The headphone device according to any one of (7) to (9), wherein the support
member includes a plurality of links and a joint portion that movably connects the
plurality of links.
- (11) The headphone device according to any one of (7) to (10), wherein the one end
of the support member is connected to a sliding member that slides on a wall portion
of the housing.
- (12) The headphone device according to any one of (7) to (11), further comprising
an attitude control device that controls an attitude of the support member.
- (13) The headphone device according to any one of (7) to (12), wherein the holding
unit protrudes outward beyond a contact surface of an ear pad with a head of the user.
- (14) The headphone device according to (13), wherein a protruding length of the holding
unit beyond the contact surface in a non-wearing state is 30 mm or less.
- (15) The headphone device according to any one of (7) to (14), wherein the support
member is formed using an elastic body.
- (16) The headphone device according to any one of (1) to (15), wherein the signal
processing unit generates the noise cancellation signal by a noise cancellation process
of a feedback scheme using the audio input unit as a cancellation point based on the
audio signal generated by the audio input unit arranged to be separated from the housing.
- (17) The headphone device according to any one of (1) to (16), further comprising
a first audio input unit that is provided in the housing and collects audio in a space
formed by the housing, an ear pad, and a head of the user to generate an audio signal,
wherein the signal processing unit generates the noise cancellation signal by a noise
cancellation process of a feedback scheme using the first audio input unit as a cancellation
point based on the audio signal generated by the first audio input unit.
- (18) The headphone device according to any one of (1) to (17), further comprising
a second audio input unit that is provided in the housing and collects audio in a
space on an outside of the housing to generate an audio signal,
wherein the signal processing unit generates the noise cancellation signal by a noise
cancellation process of a feed forward scheme based on the audio signal generated
by the second audio input unit, and adaptively controls a filter characteristic of
the noise cancellation process of the feed forward scheme based on the audio signal
generated by the audio input unit arranged to be separated from the housing.
Reference Signs List
[0375]
- 1
- EAR
- 2
- PINNA
- 3
- CRUS OF HELIX
- 4
- CAVUM CONCHA
- 5
- EAR CANAL
- 6
- TRAGUS
- 7
- INTERTRAGIC NOTCH
- 8
- ANTITRAGUS
- 9
- EARDRUM
- 11
- FIRST CURVE
- 12
- SECOND CURVE
- 19
- BOUNDARY BETWEEN CAVUM CONCHA AND EAR CANAL
- 30
- INNER SPACE
- 31
- OUTER SPACE
- 100
- EAR HOLE OPENING DEVICE
- 110
- AUDIO OUTPUT UNIT, DRIVER
- 120
- SOUND GUIDE UNIT
- 121
- ONE END
- 122
- OTHER END
- 123
- PINCH PORTION
- 130
- HOLDING UNIT
- 131
- OPENING PORTION
- 132
- SUPPORT MEMBER
- 140
- AUDIO INFORMATION ACQUISITION UNIT
- 141
- AUDIO INPUT UNIT, MICROPHONE
- 142
- EARDRUM SOUND PRESSURE ACQUISITION UNIT
- 150
- CONTROL UNIT
- 151
- SIGNAL PROCESSING UNIT
- 153
- OPERATION CONTROL UNIT
- 155
- AUTHENTICATION UNIT
- 157
- COMMUNICATION CONTROL UNIT
- 160
- SENSOR UNIT
- 161
- RFID DEVICE
- 162
- MAGNETIC SENSOR
- 170
- WIRELESS COMMUNICATION UNIT
- 300
- HEADPHONES
- 301
- HOUSING
- 302
- EAR PAD
- 303
- HOLDING UNIT
- 304
- OPENING PORTION
- 305
- FIRST SUPPORT MEMBER
- 306
- SECOND SUPPORT MEMBER
- 307
- LINK
- 310
- AUDIO OUTPUT UNIT, DRIVER
- 320
- AUDIO INPUT UNIT, MICROPHONE
- 330
- CONTROL UNIT
- 331
- SIGNAL PROCESSING UNIT
- 333
- OPERATION CONTROL UNIT
- 340
- WIRED CONNECTION UNIT
- 341
- WINDING UNIT
- 342
- RECESS
- 350
- LINK
- 351
- JOINT PORTION
- 352
- RESTRAINING MEMBER
- 353
- SLIDING MEMBER
- 354
- RAIL
- 360
- ATTITUDE CONTROL DEVICE
- 361
- OPERATING BODY
- 362
- LINK
- 363
- JOINT PORTION
- 370
- SENSOR UNIT
- 500
- HEADPHONES
- 501
- HOUSING
- 502
- EAR PAD
- 510
- AUDIO OUTPUT UNIT, DRIVER
- 520
- AUDIO INPUT UNIT, MICROPHONE
- 530
- CONTROL UNIT
- 531
- SIGNAL PROCESSING UNIT
- 533
- OPERATION CONTROL UNIT
- 535
- COMMUNICATION CONTROL UNIT
- 540
- SENSOR UNIT
- 541
- RFID DEVICE
- 550
- WIRELESS COMMUNICATION UNIT
- 800
- TERMINAL DEVICE